/*
Format of STDIN stream:

  stream ::= cmd*;

  cmd ::= new_blob
        | new_branch
        | new_commit
        | new_tag
        ;

  new_blob ::= 'blob' lf
        mark?
    file_content;
  file_content ::= data;

  new_branch ::= 'branch' sp ref_str lf
    ('from' sp (ref_str | hexsha1 | sha1exp_str | idnum) lf)?
    lf;

  new_commit ::= 'commit' sp ref_str lf
        mark?
        ('author' sp name '<' email '>' ts tz lf)?
        'committer' sp name '<' email '>' ts tz lf
        commit_msg
    file_change*
    lf;
  commit_msg ::= data;

  file_change ::= 'M' sp mode sp (hexsha1 | idnum) sp path_str lf
                | 'D' sp path_str lf
                ;
  mode ::= '644' | '755';

  new_tag ::= 'tag' sp tag_str lf
    'from' sp (ref_str | hexsha1 | sha1exp_str | idnum) lf
        'tagger' sp name '<' email '>' ts tz lf
    tag_msg;
  tag_msg ::= data;

     # note: the first idnum in a stream should be 1 and subsequent
     # idnums should not have gaps between values as this will cause
     # the stream parser to reserve space for the gapped values.  An
         # idnum can be updated in the future to a new object by issuing
     # a new mark directive with the old idnum.
         #
  mark ::= 'mark' sp idnum lf;

     # note: declen indicates the length of binary_data in bytes.
     # declen does not include the lf preceeding or trailing the
     # binary data.
     #
  data ::= 'data' sp declen lf
    binary_data
        lf;

     # note: quoted strings are C-style quoting supporting \c for
     # common escapes of 'c' (e..g \n, \t, \\, \") or \nnn where nnn
         # is the signed byte value in octal.  Note that the only
     # characters which must actually be escaped to protect the
     # stream formatting is: \, " and LF.  Otherwise these values
         # are UTF8.
     #
  ref_str     ::= ref     | '"' quoted(ref)     '"' ;
  sha1exp_str ::= sha1exp | '"' quoted(sha1exp) '"' ;
  tag_str     ::= tag     | '"' quoted(tag)     '"' ;
  path_str    ::= path    | '"' quoted(path)    '"' ;

  declen ::= # unsigned 32 bit value, ascii base10 notation;
  binary_data ::= # file content, not interpreted;

  sp ::= # ASCII space character;
  lf ::= # ASCII newline (LF) character;

     # note: a colon (':') must precede the numerical value assigned to
         # an idnum.  This is to distinguish it from a ref or tag name as
     # GIT does not permit ':' in ref or tag strings.
         #
  idnum   ::= ':' declen;
  path    ::= # GIT style file path, e.g. "a/b/c";
  ref     ::= # GIT ref name, e.g. "refs/heads/MOZ_GECKO_EXPERIMENT";
  tag     ::= # GIT tag name, e.g. "FIREFOX_1_5";
  sha1exp ::= # Any valid GIT SHA1 expression;
  hexsha1 ::= # SHA1 in hexadecimal format;

     # note: name and email are UTF8 strings, however name must not
         # contain '<' or lf and email must not contain any of the
     # following: '<', '>', lf.
         #
  name  ::= # valid GIT author/committer name;
  email ::= # valid GIT author/committer email;
  ts    ::= # time since the epoch in seconds, ascii base10 notation;
  tz    ::= # GIT style timezone;
*/

#include "builtin.h"
#include "cache.h"
#include "object.h"
#include "blob.h"
#include "tree.h"
#include "delta.h"
#include "pack.h"
#include "refs.h"
#include "csum-file.h"
#include "strbuf.h"
#include "quote.h"

struct object_entry
{
        struct object_entry *next;
        enum object_type type;
        unsigned long offset;
        unsigned char sha1[20];
};

struct object_entry_pool
{
        struct object_entry_pool *next_pool;
        struct object_entry *next_free;
        struct object_entry *end;
        struct object_entry entries[FLEX_ARRAY]; /* more */
};

struct mark_set
{
        int shift;
        union {
                struct object_entry *marked[1024];
                struct mark_set *sets[1024];
        } data;
};

struct last_object
{
        void *data;
        unsigned int len;
        unsigned int depth;
        unsigned char sha1[20];
};

struct mem_pool
{
        struct mem_pool *next_pool;
        char *next_free;
        char *end;
        char space[FLEX_ARRAY]; /* more */
};

struct atom_str
{
        struct atom_str *next_atom;
        int str_len;
        char str_dat[FLEX_ARRAY]; /* more */
};

struct tree_content;
struct tree_entry
{
        struct tree_content *tree;
        struct atom_str* name;
        unsigned int mode;
        unsigned char sha1[20];
};

struct tree_content
{
        unsigned int entry_capacity; /* must match avail_tree_content */
        unsigned int entry_count;
        struct tree_entry *entries[FLEX_ARRAY]; /* more */
};

struct avail_tree_content
{
        unsigned int entry_capacity; /* must match tree_content */
        struct avail_tree_content *next_avail;
};

struct branch
{
        struct branch *table_next_branch;
        struct branch *active_next_branch;
        const char *name;
        unsigned long last_commit;
        struct tree_entry branch_tree;
        unsigned char sha1[20];
};


/* Stats and misc. counters */
static unsigned long max_depth = 10;
static unsigned long alloc_count;
static unsigned long branch_count;
static unsigned long branch_load_count;
static unsigned long object_count;
static unsigned long duplicate_count;
static unsigned long marks_set_count;
static unsigned long object_count_by_type[9];
static unsigned long duplicate_count_by_type[9];

/* Memory pools */
static size_t mem_pool_alloc = 2*1024*1024 - sizeof(struct mem_pool);
static size_t total_allocd;
static struct mem_pool *mem_pool;

/* Atom management */
static unsigned int atom_table_sz = 4451;
static unsigned int atom_cnt;
static struct atom_str **atom_table;

/* The .pack file being generated */
static int pack_fd;
static unsigned long pack_offset;
static unsigned char pack_sha1[20];

/* Table of objects we've written. */
static unsigned int object_entry_alloc = 1000;
static struct object_entry_pool *blocks;
static struct object_entry *object_table[1 << 16];
static struct mark_set *marks;

/* Our last blob */
static struct last_object last_blob;

/* Tree management */
static unsigned int tree_entry_alloc = 1000;
static void *avail_tree_entry;
static unsigned int avail_tree_table_sz = 100;
static struct avail_tree_content **avail_tree_table;

/* Branch data */
static unsigned long max_active_branches = 5;
static unsigned long cur_active_branches;
static unsigned long branch_table_sz = 1039;
static struct branch **branch_table;
static struct branch *active_branches;

/* Input stream parsing */
static struct strbuf command_buf;
static unsigned long next_mark;


static void alloc_objects(int cnt)
{
        struct object_entry_pool *b;

        b = xmalloc(sizeof(struct object_entry_pool)
                + cnt * sizeof(struct object_entry));
        b->next_pool = blocks;
        b->next_free = b->entries;
        b->end = b->entries + cnt;
        blocks = b;
        alloc_count += cnt;
}

static struct object_entry* new_object(unsigned char *sha1)
{
        struct object_entry *e;

        if (blocks->next_free == blocks->end)
                alloc_objects(object_entry_alloc);

        e = blocks->next_free++;
        memcpy(e->sha1, sha1, sizeof(e->sha1));
        return e;
}

static struct object_entry* find_object(unsigned char *sha1)
{
        unsigned int h = sha1[0] << 8 | sha1[1];
        struct object_entry *e;
        for (e = object_table[h]; e; e = e->next)
                if (!memcmp(sha1, e->sha1, sizeof(e->sha1)))
                        return e;
        return NULL;
}

static struct object_entry* insert_object(unsigned char *sha1)
{
        unsigned int h = sha1[0] << 8 | sha1[1];
        struct object_entry *e = object_table[h];
        struct object_entry *p = NULL;

        while (e) {
                if (!memcmp(sha1, e->sha1, sizeof(e->sha1)))
                        return e;
                p = e;
                e = e->next;
        }

        e = new_object(sha1);
        e->next = NULL;
        e->offset = 0;
        if (p)
                p->next = e;
        else
                object_table[h] = e;
        return e;
}

static unsigned int hc_str(const char *s, size_t len)
{
        unsigned int r = 0;
        while (len-- > 0)
                r = r * 31 + *s++;
        return r;
}

static void* pool_alloc(size_t len)
{
        struct mem_pool *p;
        void *r;

        for (p = mem_pool; p; p = p->next_pool)
                if ((p->end - p->next_free >= len))
                        break;

        if (!p) {
                if (len >= (mem_pool_alloc/2)) {
                        total_allocd += len;
                        return xmalloc(len);
                }
                total_allocd += sizeof(struct mem_pool) + mem_pool_alloc;
                p = xmalloc(sizeof(struct mem_pool) + mem_pool_alloc);
                p->next_pool = mem_pool;
                p->next_free = p->space;
                p->end = p->next_free + mem_pool_alloc;
                mem_pool = p;
        }

        r = p->next_free;
        p->next_free += len;
        return r;
}

static void* pool_calloc(size_t count, size_t size)
{
        size_t len = count * size;
        void *r = pool_alloc(len);
        memset(r, 0, len);
        return r;
}

static char* pool_strdup(const char *s)
{
        char *r = pool_alloc(strlen(s) + 1);
        strcpy(r, s);
        return r;
}

static void insert_mark(unsigned long idnum, struct object_entry *oe)
{
        struct mark_set *s = marks;
        while ((idnum >> s->shift) >= 1024) {
                s = pool_calloc(1, sizeof(struct mark_set));
                s->shift = marks->shift + 10;
                s->data.sets[0] = marks;
                marks = s;
        }
        while (s->shift) {
                unsigned long i = idnum >> s->shift;
                idnum -= i << s->shift;
                if (!s->data.sets[i]) {
                        s->data.sets[i] = pool_calloc(1, sizeof(struct mark_set));
                        s->data.sets[i]->shift = s->shift - 10;
                }
                s = s->data.sets[i];
        }
        if (!s->data.marked[idnum])
                marks_set_count++;
        s->data.marked[idnum] = oe;
}

static struct object_entry* find_mark(unsigned long idnum)
{
        unsigned long orig_idnum = idnum;
        struct mark_set *s = marks;
        struct object_entry *oe = NULL;
        if ((idnum >> s->shift) < 1024) {
                while (s && s->shift) {
                        unsigned long i = idnum >> s->shift;
                        idnum -= i << s->shift;
                        s = s->data.sets[i];
                }
                if (s)
                        oe = s->data.marked[idnum];
        }
        if (!oe)
                die("mark :%lu not declared", orig_idnum);
        return oe;
}

static struct atom_str* to_atom(const char *s, size_t len)
{
        unsigned int hc = hc_str(s, len) % atom_table_sz;
        struct atom_str *c;

        for (c = atom_table[hc]; c; c = c->next_atom)
                if (c->str_len == len && !strncmp(s, c->str_dat, len))
                        return c;

        c = pool_alloc(sizeof(struct atom_str) + len + 1);
        c->str_len = len;
        strncpy(c->str_dat, s, len);
        c->str_dat[len] = 0;
        c->next_atom = atom_table[hc];
        atom_table[hc] = c;
        atom_cnt++;
        return c;
}

static struct branch* lookup_branch(const char *name)
{
        unsigned int hc = hc_str(name, strlen(name)) % branch_table_sz;
        struct branch *b;

        for (b = branch_table[hc]; b; b = b->table_next_branch)
                if (!strcmp(name, b->name))
                        return b;
        return NULL;
}

static struct branch* new_branch(const char *name)
{
        unsigned int hc = hc_str(name, strlen(name)) % branch_table_sz;
        struct branch* b = lookup_branch(name);

        if (b)
                die("Invalid attempt to create duplicate branch: %s", name);
        if (check_ref_format(name))
                die("Branch name doesn't conform to GIT standards: %s", name);

        b = pool_calloc(1, sizeof(struct branch));
        b->name = pool_strdup(name);
        b->table_next_branch = branch_table[hc];
        branch_table[hc] = b;
        branch_count++;
        return b;
}

static unsigned int hc_entries(unsigned int cnt)
{
        cnt = cnt & 7 ? (cnt / 8) + 1 : cnt / 8;
        return cnt < avail_tree_table_sz ? cnt : avail_tree_table_sz - 1;
}

static struct tree_content* new_tree_content(unsigned int cnt)
{
        struct avail_tree_content *f, *l = NULL;
        struct tree_content *t;
        unsigned int hc = hc_entries(cnt);

        for (f = avail_tree_table[hc]; f; l = f, f = f->next_avail)
                if (f->entry_capacity >= cnt)
                        break;

        if (f) {
                if (l)
                        l->next_avail = f->next_avail;
                else
                        avail_tree_table[hc] = f->next_avail;
        } else {
                cnt = cnt & 7 ? ((cnt / 8) + 1) * 8 : cnt;
                f = pool_alloc(sizeof(*t) + sizeof(t->entries[0]) * cnt);
                f->entry_capacity = cnt;
        }

        t = (struct tree_content*)f;
        t->entry_count = 0;
        return t;
}

static void release_tree_entry(struct tree_entry *e);
static void release_tree_content(struct tree_content *t)
{
        struct avail_tree_content *f = (struct avail_tree_content*)t;
        unsigned int hc = hc_entries(f->entry_capacity);
        f->next_avail = avail_tree_table[hc];
        avail_tree_table[hc] = f;
}

static void release_tree_content_recursive(struct tree_content *t)
{
        unsigned int i;
        for (i = 0; i < t->entry_count; i++)
                release_tree_entry(t->entries[i]);
        release_tree_content(t);
}

static struct tree_content* grow_tree_content(
        struct tree_content *t,
        int amt)
{
        struct tree_content *r = new_tree_content(t->entry_count + amt);
        r->entry_count = t->entry_count;
        memcpy(r->entries,t->entries,t->entry_count*sizeof(t->entries[0]));
        release_tree_content(t);
        return r;
}

static struct tree_entry* new_tree_entry()
{
        struct tree_entry *e;

        if (!avail_tree_entry) {
                unsigned int n = tree_entry_alloc;
                avail_tree_entry = e = xmalloc(n * sizeof(struct tree_entry));
                while (n--) {
                        *((void**)e) = e + 1;
                        e++;
                }
        }

        e = avail_tree_entry;
        avail_tree_entry = *((void**)e);
        return e;
}

static void release_tree_entry(struct tree_entry *e)
{
        if (e->tree)
                release_tree_content_recursive(e->tree);
        *((void**)e) = avail_tree_entry;
        avail_tree_entry = e;
}

static void yread(int fd, void *buffer, size_t length)
{
        ssize_t ret = 0;
        while (ret < length) {
                ssize_t size = xread(fd, (char *) buffer + ret, length - ret);
                if (!size)
                        die("Read from descriptor %i: end of stream", fd);
                if (size < 0)
                        die("Read from descriptor %i: %s", fd, strerror(errno));
                ret += size;
        }
}

static void ywrite(int fd, void *buffer, size_t length)
{
        ssize_t ret = 0;
        while (ret < length) {
                ssize_t size = xwrite(fd, (char *) buffer + ret, length - ret);
                if (!size)
                        die("Write to descriptor %i: end of file", fd);
                if (size < 0)
                        die("Write to descriptor %i: %s", fd, strerror(errno));
                ret += size;
        }
}

static size_t encode_header(
        enum object_type type,
        size_t size,
        unsigned char *hdr)
{
        int n = 1;
        unsigned char c;

        if (type < OBJ_COMMIT || type > OBJ_DELTA)
                die("bad type %d", type);

        c = (type << 4) | (size & 15);
        size >>= 4;
        while (size) {
                *hdr++ = c | 0x80;
                c = size & 0x7f;
                size >>= 7;
                n++;
        }
        *hdr = c;
        return n;
}

static int store_object(
        enum object_type type,
        void *dat,
        size_t datlen,
        struct last_object *last,
        unsigned char *sha1out,
        unsigned long mark)
{
        void *out, *delta;
        struct object_entry *e;
        unsigned char hdr[96];
        unsigned char sha1[20];
        unsigned long hdrlen, deltalen;
        SHA_CTX c;
        z_stream s;

        hdrlen = sprintf((char*)hdr,"%s %lu",type_names[type],datlen) + 1;
        SHA1_Init(&c);
        SHA1_Update(&c, hdr, hdrlen);
        SHA1_Update(&c, dat, datlen);
        SHA1_Final(sha1, &c);
        if (sha1out)
                memcpy(sha1out, sha1, sizeof(sha1));

        e = insert_object(sha1);
        if (mark)
                insert_mark(mark, e);
        if (e->offset) {
                duplicate_count++;
                duplicate_count_by_type[type]++;
                return 1;
        }
        e->type = type;
        e->offset = pack_offset;
        object_count++;
        object_count_by_type[type]++;

        if (last && last->data && last->depth < max_depth)
                delta = diff_delta(last->data, last->len,
                        dat, datlen,
                        &deltalen, 0);
        else
                delta = 0;

        memset(&s, 0, sizeof(s));
        deflateInit(&s, zlib_compression_level);

        if (delta) {
                last->depth++;
                s.next_in = delta;
                s.avail_in = deltalen;
                hdrlen = encode_header(OBJ_DELTA, deltalen, hdr);
                ywrite(pack_fd, hdr, hdrlen);
                ywrite(pack_fd, last->sha1, sizeof(sha1));
                pack_offset += hdrlen + sizeof(sha1);
        } else {
                if (last)
                        last->depth = 0;
                s.next_in = dat;
                s.avail_in = datlen;
                hdrlen = encode_header(type, datlen, hdr);
                ywrite(pack_fd, hdr, hdrlen);
                pack_offset += hdrlen;
        }

        s.avail_out = deflateBound(&s, s.avail_in);
        s.next_out = out = xmalloc(s.avail_out);
        while (deflate(&s, Z_FINISH) == Z_OK)
                /* nothing */;
        deflateEnd(&s);

        ywrite(pack_fd, out, s.total_out);
        pack_offset += s.total_out;

        free(out);
        if (delta)
                free(delta);
        if (last) {
                if (last->data)
                        free(last->data);
                last->data = dat;
                last->len = datlen;
                memcpy(last->sha1, sha1, sizeof(sha1));
        }
        return 0;
}

static const char *get_mode(const char *str, unsigned int *modep)
{
        unsigned char c;
        unsigned int mode = 0;

        while ((c = *str++) != ' ') {
                if (c < '0' || c > '7')
                        return NULL;
                mode = (mode << 3) + (c - '0');
        }
        *modep = mode;
        return str;
}

static void load_tree(struct tree_entry *root)
{
        struct object_entry *myoe;
        struct tree_content *t;
        unsigned long size;
        char *buf;
        const char *c;
        char type[20];

        root->tree = t = new_tree_content(8);
        if (!memcmp(root->sha1, null_sha1, 20))
                return;

        myoe = find_object(root->sha1);
        if (myoe) {
                die("FIXME");
        } else {
                buf = read_sha1_file(root->sha1, type, &size);
                if (!buf || strcmp(type, tree_type))
                        die("Can't load existing tree %s", sha1_to_hex(root->sha1));
        }

        c = buf;
        while (c != (buf + size)) {
                struct tree_entry *e = new_tree_entry();

                if (t->entry_count == t->entry_capacity)
                        root->tree = t = grow_tree_content(t, 8);
                t->entries[t->entry_count++] = e;

                e->tree = NULL;
                c = get_mode(c, &e->mode);
                if (!c)
                        die("Corrupt mode in %s", sha1_to_hex(root->sha1));
                e->name = to_atom(c, strlen(c));
                c += e->name->str_len + 1;
                memcpy(e->sha1, c, sizeof(e->sha1));
                c += 20;
        }
        free(buf);
}

static int tecmp (const void *_a, const void *_b)
{
        struct tree_entry *a = *((struct tree_entry**)_a);
        struct tree_entry *b = *((struct tree_entry**)_b);
        return base_name_compare(
                a->name->str_dat, a->name->str_len, a->mode,
                b->name->str_dat, b->name->str_len, b->mode);
}

static void store_tree(struct tree_entry *root)
{
        struct tree_content *t = root->tree;
        unsigned int i;
        size_t maxlen;
        char *buf, *c;

        if (memcmp(root->sha1, null_sha1, 20))
                return;

        maxlen = 0;
        for (i = 0; i < t->entry_count; i++) {
                maxlen += t->entries[i]->name->str_len + 34;
                if (t->entries[i]->tree)
                        store_tree(t->entries[i]);
        }

        qsort(t->entries, t->entry_count, sizeof(t->entries[0]), tecmp);
        buf = c = xmalloc(maxlen);
        for (i = 0; i < t->entry_count; i++) {
                struct tree_entry *e = t->entries[i];
                c += sprintf(c, "%o", e->mode);
                *c++ = ' ';
                strcpy(c, e->name->str_dat);
                c += e->name->str_len + 1;
                memcpy(c, e->sha1, 20);
                c += 20;
        }
        store_object(OBJ_TREE, buf, c - buf, NULL, root->sha1, 0);
        free(buf);
}

static int tree_content_set(
        struct tree_entry *root,
        const char *p,
        const unsigned char *sha1,
        const unsigned int mode)
{
        struct tree_content *t = root->tree;
        const char *slash1;
        unsigned int i, n;
        struct tree_entry *e;

        slash1 = strchr(p, '/');
        if (slash1)
                n = slash1 - p;
        else
                n = strlen(p);

        for (i = 0; i < t->entry_count; i++) {
                e = t->entries[i];
                if (e->name->str_len == n && !strncmp(p, e->name->str_dat, n)) {
                        if (!slash1) {
                                if (e->mode == mode && !memcmp(e->sha1, sha1, 20))
                                        return 0;
                                e->mode = mode;
                                memcpy(e->sha1, sha1, 20);
                                if (e->tree) {
                                        release_tree_content_recursive(e->tree);
                                        e->tree = NULL;
                                }
                                memcpy(root->sha1, null_sha1, 20);
                                return 1;
                        }
                        if (!S_ISDIR(e->mode)) {
                                e->tree = new_tree_content(8);
                                e->mode = S_IFDIR;
                        }
                        if (!e->tree)
                                load_tree(e);
                        if (tree_content_set(e, slash1 + 1, sha1, mode)) {
                                memcpy(root->sha1, null_sha1, 20);
                                return 1;
                        }
                        return 0;
                }
        }

        if (t->entry_count == t->entry_capacity)
                root->tree = t = grow_tree_content(t, 8);
        e = new_tree_entry();
        e->name = to_atom(p, n);
        t->entries[t->entry_count++] = e;
        if (slash1) {
                e->tree = new_tree_content(8);
                e->mode = S_IFDIR;
                tree_content_set(e, slash1 + 1, sha1, mode);
        } else {
                e->tree = NULL;
                e->mode = mode;
                memcpy(e->sha1, sha1, 20);
        }
        memcpy(root->sha1, null_sha1, 20);
        return 1;
}

static int tree_content_remove(struct tree_entry *root, const char *p)
{
        struct tree_content *t = root->tree;
        const char *slash1;
        unsigned int i, n;
        struct tree_entry *e;

        slash1 = strchr(p, '/');
        if (slash1)
                n = slash1 - p;
        else
                n = strlen(p);

        for (i = 0; i < t->entry_count; i++) {
                e = t->entries[i];
                if (e->name->str_len == n && !strncmp(p, e->name->str_dat, n)) {
                        if (!slash1 || !S_ISDIR(e->mode))
                                goto del_entry;
                        if (!e->tree)
                                load_tree(e);
                        if (tree_content_remove(e, slash1 + 1)) {
                                if (!e->tree->entry_count)
                                        goto del_entry;
                                memcpy(root->sha1, null_sha1, 20);
                                return 1;
                        }
                        return 0;
                }
        }
        return 0;

del_entry:
        for (i++; i < t->entry_count; i++)
                t->entries[i-1] = t->entries[i];
        t->entry_count--;
        release_tree_entry(e);
        memcpy(root->sha1, null_sha1, 20);
        return 1;
}

static void init_pack_header()
{
        struct pack_header hdr;

        hdr.hdr_signature = htonl(PACK_SIGNATURE);
        hdr.hdr_version = htonl(2);
        hdr.hdr_entries = 0;

        ywrite(pack_fd, &hdr, sizeof(hdr));
        pack_offset = sizeof(hdr);
}

static void fixup_header_footer()
{
        SHA_CTX c;
        char hdr[8];
        unsigned long cnt;
        char *buf;
        size_t n;

        if (lseek(pack_fd, 0, SEEK_SET) != 0)
                die("Failed seeking to start: %s", strerror(errno));

        SHA1_Init(&c);
        yread(pack_fd, hdr, 8);
        SHA1_Update(&c, hdr, 8);

        cnt = htonl(object_count);
        SHA1_Update(&c, &cnt, 4);
        ywrite(pack_fd, &cnt, 4);

        buf = xmalloc(128 * 1024);
        for (;;) {
                n = xread(pack_fd, buf, 128 * 1024);
                if (n <= 0)
                        break;
                SHA1_Update(&c, buf, n);
        }
        free(buf);

        SHA1_Final(pack_sha1, &c);
        ywrite(pack_fd, pack_sha1, sizeof(pack_sha1));
}

static int oecmp (const void *_a, const void *_b)
{
        struct object_entry *a = *((struct object_entry**)_a);
        struct object_entry *b = *((struct object_entry**)_b);
        return memcmp(a->sha1, b->sha1, sizeof(a->sha1));
}

static void write_index(const char *idx_name)
{
        struct sha1file *f;
        struct object_entry **idx, **c, **last;
        struct object_entry *e;
        struct object_entry_pool *o;
        unsigned int array[256];
        int i;

        /* Build the sorted table of object IDs. */
        idx = xmalloc(object_count * sizeof(struct object_entry*));
        c = idx;
        for (o = blocks; o; o = o->next_pool)
                for (e = o->entries; e != o->next_free; e++)
                        *c++ = e;
        last = idx + object_count;
        qsort(idx, object_count, sizeof(struct object_entry*), oecmp);

        /* Generate the fan-out array. */
        c = idx;
        for (i = 0; i < 256; i++) {
                struct object_entry **next = c;;
                while (next < last) {
                        if ((*next)->sha1[0] != i)
                                break;
                        next++;
                }
                array[i] = htonl(next - idx);
                c = next;
        }

        f = sha1create("%s", idx_name);
        sha1write(f, array, 256 * sizeof(int));
        for (c = idx; c != last; c++) {
                unsigned int offset = htonl((*c)->offset);
                sha1write(f, &offset, 4);
                sha1write(f, (*c)->sha1, sizeof((*c)->sha1));
        }
        sha1write(f, pack_sha1, sizeof(pack_sha1));
        sha1close(f, NULL, 1);
        free(idx);
}

static void dump_branches()
{
        static const char *msg = "fast-import";
        unsigned int i;
        struct branch *b;
        struct ref_lock *lock;

        for (i = 0; i < branch_table_sz; i++) {
                for (b = branch_table[i]; b; b = b->table_next_branch) {
                        lock = lock_any_ref_for_update(b->name, NULL, 0);
                        if (!lock || write_ref_sha1(lock, b->sha1, msg) < 0)
                                die("Can't write %s", b->name);
                }
        }
}

static void read_next_command()
{
        read_line(&command_buf, stdin, '\n');
}

static void cmd_mark()
{
        if (!strncmp("mark :", command_buf.buf, 6)) {
                next_mark = strtoul(command_buf.buf + 6, NULL, 10);
                read_next_command();
        }
        else
                next_mark = 0;
}

static void* cmd_data (size_t *size)
{
        size_t n = 0;
        void *buffer;
        size_t length;

        if (strncmp("data ", command_buf.buf, 5))
                die("Expected 'data n' command, found: %s", command_buf.buf);

        length = strtoul(command_buf.buf + 5, NULL, 10);
        buffer = xmalloc(length);

        while (n < length) {
                size_t s = fread((char*)buffer + n, 1, length - n, stdin);
                if (!s && feof(stdin))
                        die("EOF in data (%lu bytes remaining)", length - n);
                n += s;
        }

        if (fgetc(stdin) != '\n')
                die("An lf did not trail the binary data as expected.");

        *size = length;
        return buffer;
}

static void cmd_new_blob()
{
        size_t l;
        void *d;

        read_next_command();
        cmd_mark();
        d = cmd_data(&l);

        if (store_object(OBJ_BLOB, d, l, &last_blob, NULL, next_mark))
                free(d);
}

static void unload_one_branch()
{
        while (cur_active_branches >= max_active_branches) {
                unsigned long min_commit = ULONG_MAX;
                struct branch *e, *l = NULL, *p = NULL;

                for (e = active_branches; e; e = e->active_next_branch) {
                        if (e->last_commit < min_commit) {
                                p = l;
                                min_commit = e->last_commit;
                        }
                        l = e;
                }

                if (p) {
                        e = p->active_next_branch;
                        p->active_next_branch = e->active_next_branch;
                } else {
                        e = active_branches;
                        active_branches = e->active_next_branch;
                }
                e->active_next_branch = NULL;
                if (e->branch_tree.tree) {
                        release_tree_content_recursive(e->branch_tree.tree);
                        e->branch_tree.tree = NULL;
                }
                cur_active_branches--;
        }
}

static void load_branch(struct branch *b)
{
        load_tree(&b->branch_tree);
        b->active_next_branch = active_branches;
        active_branches = b;
        cur_active_branches++;
        branch_load_count++;
}

static void file_change_m(struct branch *b)
{
        const char *p = command_buf.buf + 2;
        char *p_uq;
        const char *endp;
        struct object_entry *oe;
        unsigned char sha1[20];
        unsigned int mode;
        char type[20];

        p = get_mode(p, &mode);
        if (!p)
                die("Corrupt mode: %s", command_buf.buf);
        switch (mode) {
        case S_IFREG | 0644:
        case S_IFREG | 0755:
        case S_IFLNK:
        case 0644:
        case 0755:
                /* ok */
                break;
        default:
                die("Corrupt mode: %s", command_buf.buf);
        }

        if (*p == ':') {
                char *x;
                oe = find_mark(strtoul(p + 1, &x, 10));
                p = x;
        } else {
                if (get_sha1_hex(p, sha1))
                        die("Invalid SHA1: %s", command_buf.buf);
                oe = find_object(sha1);
                p += 40;
        }
        if (*p++ != ' ')
                die("Missing space after SHA1: %s", command_buf.buf);

        p_uq = unquote_c_style(p, &endp);
        if (p_uq) {
                if (*endp)
                        die("Garbage after path in: %s", command_buf.buf);
                p = p_uq;
        }

        if (oe) {
                if (oe->type != OBJ_BLOB)
                        die("Not a blob (actually a %s): %s",
                                command_buf.buf, type_names[oe->type]);
        } else {
                if (sha1_object_info(sha1, type, NULL))
                        die("Blob not found: %s", command_buf.buf);
                if (strcmp(blob_type, type))
                        die("Not a blob (actually a %s): %s",
                                command_buf.buf, type);
        }

        tree_content_set(&b->branch_tree, p, sha1, S_IFREG | mode);

        if (p_uq)
                free(p_uq);
}

static void file_change_d(struct branch *b)
{
        const char *p = command_buf.buf + 2;
        char *p_uq;
        const char *endp;

        p_uq = unquote_c_style(p, &endp);
        if (p_uq) {
                if (*endp)
                        die("Garbage after path in: %s", command_buf.buf);
                p = p_uq;
        }
        tree_content_remove(&b->branch_tree, p);
        if (p_uq)
                free(p_uq);
}

static void cmd_new_commit()
{
        struct branch *b;
        void *msg;
        size_t msglen;
        char *str_uq;
        const char *endp;
        char *sp;
        char *author = NULL;
        char *committer = NULL;
        char *body;

        /* Obtain the branch name from the rest of our command */
        sp = strchr(command_buf.buf, ' ') + 1;
        str_uq = unquote_c_style(sp, &endp);
        if (str_uq) {
                if (*endp)
                        die("Garbage after ref in: %s", command_buf.buf);
                sp = str_uq;
        }
        b = lookup_branch(sp);
        if (!b)
                die("Branch not declared: %s", sp);
        if (str_uq)
                free(str_uq);

        read_next_command();
        cmd_mark();
        if (!strncmp("author ", command_buf.buf, 7)) {
                author = strdup(command_buf.buf);
                read_next_command();
        }
        if (!strncmp("committer ", command_buf.buf, 10)) {
                committer = strdup(command_buf.buf);
                read_next_command();
        }
        if (!committer)
                die("Expected committer but didn't get one");
        msg = cmd_data(&msglen);

        /* ensure the branch is active/loaded */
        if (!b->branch_tree.tree) {
                unload_one_branch();
                load_branch(b);
        }

        /* file_change* */
        for (;;) {
                read_next_command();
                if (1 == command_buf.len)
                        break;
                else if (!strncmp("M ", command_buf.buf, 2))
                        file_change_m(b);
                else if (!strncmp("D ", command_buf.buf, 2))
                        file_change_d(b);
                else
                        die("Unsupported file_change: %s", command_buf.buf);
        }

        /* build the tree and the commit */
        store_tree(&b->branch_tree);
        body = xmalloc(97 + msglen
                + (author
                        ? strlen(author) + strlen(committer)
                        : 2 * strlen(committer)));
        sp = body;
        sp += sprintf(sp, "tree %s\n", sha1_to_hex(b->branch_tree.sha1));
        if (memcmp(b->sha1, null_sha1, 20))
                sp += sprintf(sp, "parent %s\n", sha1_to_hex(b->sha1));
        if (author)
                sp += sprintf(sp, "%s\n", author);
        else
                sp += sprintf(sp, "author %s\n", committer + 10);
        sp += sprintf(sp, "%s\n\n", committer);
        memcpy(sp, msg, msglen);
        sp += msglen;
        if (author)
                free(author);
        free(committer);
        free(msg);

        store_object(OBJ_COMMIT, body, sp - body, NULL, b->sha1, next_mark);
        free(body);
        b->last_commit = object_count_by_type[OBJ_COMMIT];
}

static void cmd_new_branch()
{
        struct branch *b;
        char *str_uq;
        const char *endp;
        char *sp;

        /* Obtain the new branch name from the rest of our command */
        sp = strchr(command_buf.buf, ' ') + 1;
        str_uq = unquote_c_style(sp, &endp);
        if (str_uq) {
                if (*endp)
                        die("Garbage after ref in: %s", command_buf.buf);
                sp = str_uq;
        }
        b = new_branch(sp);
        if (str_uq)
                free(str_uq);
        read_next_command();

        /* from ... */
        if (!strncmp("from ", command_buf.buf, 5)) {
                const char *from;
                struct branch *s;

                from = strchr(command_buf.buf, ' ') + 1;
                str_uq = unquote_c_style(from, &endp);
                if (str_uq) {
                        if (*endp)
                                die("Garbage after string in: %s", command_buf.buf);
                        from = str_uq;
                }

                s = lookup_branch(from);
                if (b == s)
                        die("Can't create a branch from itself: %s", b->name);
                else if (s) {
                        memcpy(b->sha1, s->sha1, 20);
                        memcpy(b->branch_tree.sha1, s->branch_tree.sha1, 20);
                } else if (*from == ':') {
                        unsigned long idnum = strtoul(from + 1, NULL, 10);
                        struct object_entry *oe = find_mark(idnum);
                        if (oe->type != OBJ_COMMIT)
                                die("Mark :%lu not a commit", idnum);
                        memcpy(b->sha1, oe->sha1, 20);
                        memcpy(b->branch_tree.sha1, null_sha1, 20);
                } else if (!get_sha1(from, b->sha1)) {
                        if (!memcmp(b->sha1, null_sha1, 20))
                                memcpy(b->branch_tree.sha1, null_sha1, 20);
                        else {
                                unsigned long size;
                                char *buf;

                                buf = read_object_with_reference(b->sha1,
                                        type_names[OBJ_COMMIT], &size, b->sha1);
                                if (!buf || size < 46)
                                        die("Not a valid commit: %s", from);
                                if (memcmp("tree ", buf, 5)
                                        || get_sha1_hex(buf + 5, b->branch_tree.sha1))
                                        die("The commit %s is corrupt", sha1_to_hex(b->sha1));
                                free(buf);
                        }
                } else
                        die("Invalid ref name or SHA1 expression: %s", from);

                if (str_uq)
                        free(str_uq);
                read_next_command();
        } else {
                memcpy(b->sha1, null_sha1, 20);
                memcpy(b->branch_tree.sha1, null_sha1, 20);
        }

        if (command_buf.eof || command_buf.len > 1)
                die("An lf did not terminate the branch command as expected.");
}

static const char fast_import_usage[] =
"git-fast-import [--objects=n] [--depth=n] [--active-branches=n] temp.pack";

int main(int argc, const char **argv)
{
        const char *base_name;
        int i;
        unsigned long est_obj_cnt = 1000;
        char *pack_name;
        char *idx_name;
        struct stat sb;

        setup_ident();
        git_config(git_default_config);

        for (i = 1; i < argc; i++) {
                const char *a = argv[i];

                if (*a != '-' || !strcmp(a, "--"))
                        break;
                else if (!strncmp(a, "--objects=", 10))
                        est_obj_cnt = strtoul(a + 10, NULL, 0);
                else if (!strncmp(a, "--depth=", 8))
                        max_depth = strtoul(a + 8, NULL, 0);
                else if (!strncmp(a, "--active-branches=", 18))
                        max_active_branches = strtoul(a + 18, NULL, 0);
                else
                        die("unknown option %s", a);
        }
        if ((i+1) != argc)
                usage(fast_import_usage);
        base_name = argv[i];

        pack_name = xmalloc(strlen(base_name) + 6);
        sprintf(pack_name, "%s.pack", base_name);
        idx_name = xmalloc(strlen(base_name) + 5);
        sprintf(idx_name, "%s.idx", base_name);

        pack_fd = open(pack_name, O_RDWR|O_CREAT|O_EXCL, 0666);
        if (pack_fd < 0)
                die("Can't create %s: %s", pack_name, strerror(errno));

        init_pack_header();
        alloc_objects(est_obj_cnt);
        strbuf_init(&command_buf);

        atom_table = xcalloc(atom_table_sz, sizeof(struct atom_str*));
        branch_table = xcalloc(branch_table_sz, sizeof(struct branch*));
        avail_tree_table = xcalloc(avail_tree_table_sz, sizeof(struct avail_tree_content*));
        marks = pool_calloc(1, sizeof(struct mark_set));

        for (;;) {
                read_next_command();
                if (command_buf.eof)
                        break;
                else if (!strcmp("blob", command_buf.buf))
                        cmd_new_blob();
                else if (!strncmp("branch ", command_buf.buf, 7))
                        cmd_new_branch();
                else if (!strncmp("commit ", command_buf.buf, 7))
                        cmd_new_commit();
                else
                        die("Unsupported command: %s", command_buf.buf);
        }

        fixup_header_footer();
        close(pack_fd);
        write_index(idx_name);
        dump_branches();

        fprintf(stderr, "%s statistics:\n", argv[0]);
        fprintf(stderr, "---------------------------------------------------\n");
        fprintf(stderr, "Alloc'd objects: %10lu (%10lu overflow  )\n", alloc_count, alloc_count - est_obj_cnt);
        fprintf(stderr, "Total objects:   %10lu (%10lu duplicates)\n", object_count, duplicate_count);
        fprintf(stderr, "      blobs  :   %10lu (%10lu duplicates)\n", object_count_by_type[OBJ_BLOB], duplicate_count_by_type[OBJ_BLOB]);
        fprintf(stderr, "      trees  :   %10lu (%10lu duplicates)\n", object_count_by_type[OBJ_TREE], duplicate_count_by_type[OBJ_TREE]);
        fprintf(stderr, "      commits:   %10lu (%10lu duplicates)\n", object_count_by_type[OBJ_COMMIT], duplicate_count_by_type[OBJ_COMMIT]);
        fprintf(stderr, "      tags   :   %10lu (%10lu duplicates)\n", object_count_by_type[OBJ_TAG], duplicate_count_by_type[OBJ_TAG]);
        fprintf(stderr, "Total branches:  %10lu (%10lu loads     )\n", branch_count, branch_load_count);
        fprintf(stderr, "      marks:     %10u (%10lu unique    )\n", (1 << marks->shift) * 1024, marks_set_count);
        fprintf(stderr, "      atoms:     %10u\n", atom_cnt);
        fprintf(stderr, "Memory total:    %10lu KiB\n", (total_allocd + alloc_count*sizeof(struct object_entry))/1024);
        fprintf(stderr, "       pools:    %10lu KiB\n", total_allocd/1024);
        fprintf(stderr, "     objects:    %10lu KiB\n", (alloc_count*sizeof(struct object_entry))/1024);
        fprintf(stderr, "---------------------------------------------------\n");

        stat(pack_name, &sb);
        fprintf(stderr, "Pack size:       %10lu KiB\n", (unsigned long)(sb.st_size/1024));
        stat(idx_name, &sb);
        fprintf(stderr, "Index size:      %10lu KiB\n", (unsigned long)(sb.st_size/1024));

        fprintf(stderr, "\n");

        return 0;
}