/*
 *  LibXDiff by Davide Libenzi ( File Differential Library )
 *  Copyright (C) 2003  Davide Libenzi
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2.1 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 *  Davide Libenzi <davidel@xmailserver.org>
 *
 */

#include <limits.h>
#include <assert.h>
#include "xinclude.h"




long xdl_bogosqrt(long n) {
        long i;

        /*
         * Classical integer square root approximation using shifts.
         */
        for (i = 1; n > 0; n >>= 2)
                i <<= 1;

        return i;
}


int xdl_emit_diffrec(char const *rec, long size, char const *pre, long psize,
                     xdemitcb_t *ecb) {
        int i = 2;
        mmbuffer_t mb[3];

        mb[0].ptr = (char *) pre;
        mb[0].size = psize;
        mb[1].ptr = (char *) rec;
        mb[1].size = size;
        if (size > 0 && rec[size - 1] != '\n') {
                mb[2].ptr = (char *) "\n\\ No newline at end of file\n";
                mb[2].size = strlen(mb[2].ptr);
                i++;
        }
        if (ecb->outf(ecb->priv, mb, i) < 0) {

                return -1;
        }

        return 0;
}

void *xdl_mmfile_first(mmfile_t *mmf, long *size)
{
        *size = mmf->size;
        return mmf->ptr;
}


long xdl_mmfile_size(mmfile_t *mmf)
{
        return mmf->size;
}


int xdl_cha_init(chastore_t *cha, long isize, long icount) {

        cha->head = cha->tail = NULL;
        cha->isize = isize;
        cha->nsize = icount * isize;
        cha->ancur = cha->sncur = NULL;
        cha->scurr = 0;

        return 0;
}


void xdl_cha_free(chastore_t *cha) {
        chanode_t *cur, *tmp;

        for (cur = cha->head; (tmp = cur) != NULL;) {
                cur = cur->next;
                xdl_free(tmp);
        }
}


void *xdl_cha_alloc(chastore_t *cha) {
        chanode_t *ancur;
        void *data;

        if (!(ancur = cha->ancur) || ancur->icurr == cha->nsize) {
                if (!(ancur = (chanode_t *) xdl_malloc(sizeof(chanode_t) + cha->nsize))) {

                        return NULL;
                }
                ancur->icurr = 0;
                ancur->next = NULL;
                if (cha->tail)
                        cha->tail->next = ancur;
                if (!cha->head)
                        cha->head = ancur;
                cha->tail = ancur;
                cha->ancur = ancur;
        }

        data = (char *) ancur + sizeof(chanode_t) + ancur->icurr;
        ancur->icurr += cha->isize;

        return data;
}

long xdl_guess_lines(mmfile_t *mf, long sample) {
        long nl = 0, size, tsize = 0;
        char const *data, *cur, *top;

        if ((cur = data = xdl_mmfile_first(mf, &size)) != NULL) {
                for (top = data + size; nl < sample && cur < top; ) {
                        nl++;
                        if (!(cur = memchr(cur, '\n', top - cur)))
                                cur = top;
                        else
                                cur++;
                }
                tsize += (long) (cur - data);
        }

        if (nl && tsize)
                nl = xdl_mmfile_size(mf) / (tsize / nl);

        return nl + 1;
}

int xdl_blankline(const char *line, long size, long flags)
{
        long i;

        if (!(flags & XDF_WHITESPACE_FLAGS))
                return (size <= 1);

        for (i = 0; i < size && XDL_ISSPACE(line[i]); i++)
                ;

        return (i == size);
}

int xdl_recmatch(const char *l1, long s1, const char *l2, long s2, long flags)
{
        int i1, i2;

        if (s1 == s2 && !memcmp(l1, l2, s1))
                return 1;
        if (!(flags & XDF_WHITESPACE_FLAGS))
                return 0;

        i1 = 0;
        i2 = 0;

        /*
         * -w matches everything that matches with -b, and -b in turn
         * matches everything that matches with --ignore-space-at-eol.
         *
         * Each flavor of ignoring needs different logic to skip whitespaces
         * while we have both sides to compare.
         */
        if (flags & XDF_IGNORE_WHITESPACE) {
                goto skip_ws;
                while (i1 < s1 && i2 < s2) {
                        if (l1[i1++] != l2[i2++])
                                return 0;
                skip_ws:
                        while (i1 < s1 && XDL_ISSPACE(l1[i1]))
                                i1++;
                        while (i2 < s2 && XDL_ISSPACE(l2[i2]))
                                i2++;
                }
        } else if (flags & XDF_IGNORE_WHITESPACE_CHANGE) {
                while (i1 < s1 && i2 < s2) {
                        if (XDL_ISSPACE(l1[i1]) && XDL_ISSPACE(l2[i2])) {
                                /* Skip matching spaces and try again */
                                while (i1 < s1 && XDL_ISSPACE(l1[i1]))
                                        i1++;
                                while (i2 < s2 && XDL_ISSPACE(l2[i2]))
                                        i2++;
                                continue;
                        }
                        if (l1[i1++] != l2[i2++])
                                return 0;
                }
        } else if (flags & XDF_IGNORE_WHITESPACE_AT_EOL) {
                while (i1 < s1 && i2 < s2 && l1[i1++] == l2[i2++])
                        ; /* keep going */
        }

        /*
         * After running out of one side, the remaining side must have
         * nothing but whitespace for the lines to match.  Note that
         * ignore-whitespace-at-eol case may break out of the loop
         * while there still are characters remaining on both lines.
         */
        if (i1 < s1) {
                while (i1 < s1 && XDL_ISSPACE(l1[i1]))
                        i1++;
                if (s1 != i1)
                        return 0;
        }
        if (i2 < s2) {
                while (i2 < s2 && XDL_ISSPACE(l2[i2]))
                        i2++;
                return (s2 == i2);
        }
        return 1;
}

static unsigned long xdl_hash_record_with_whitespace(char const **data,
                char const *top, long flags) {
        unsigned long ha = 5381;
        char const *ptr = *data;

        for (; ptr < top && *ptr != '\n'; ptr++) {
                if (XDL_ISSPACE(*ptr)) {
                        const char *ptr2 = ptr;
                        int at_eol;
                        while (ptr + 1 < top && XDL_ISSPACE(ptr[1])
                                        && ptr[1] != '\n')
                                ptr++;
                        at_eol = (top <= ptr + 1 || ptr[1] == '\n');
                        if (flags & XDF_IGNORE_WHITESPACE)
                                ; /* already handled */
                        else if (flags & XDF_IGNORE_WHITESPACE_CHANGE
                                 && !at_eol) {
                                ha += (ha << 5);
                                ha ^= (unsigned long) ' ';
                        }
                        else if (flags & XDF_IGNORE_WHITESPACE_AT_EOL
                                 && !at_eol) {
                                while (ptr2 != ptr + 1) {
                                        ha += (ha << 5);
                                        ha ^= (unsigned long) *ptr2;
                                        ptr2++;
                                }
                        }
                        continue;
                }
                ha += (ha << 5);
                ha ^= (unsigned long) *ptr;
        }
        *data = ptr < top ? ptr + 1: ptr;

        return ha;
}

#ifdef XDL_FAST_HASH

#define REPEAT_BYTE(x)  ((~0ul / 0xff) * (x))

#define ONEBYTES        REPEAT_BYTE(0x01)
#define NEWLINEBYTES    REPEAT_BYTE(0x0a)
#define HIGHBITS        REPEAT_BYTE(0x80)

/* Return the high bit set in the first byte that is a zero */
static inline unsigned long has_zero(unsigned long a)
{
        return ((a - ONEBYTES) & ~a) & HIGHBITS;
}

static inline long count_masked_bytes(unsigned long mask)
{
        if (sizeof(long) == 8) {
                /*
                 * Jan Achrenius on G+: microoptimized version of
                 * the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
                 * that works for the bytemasks without having to
                 * mask them first.
                 */
                /*
                 * return mask * 0x0001020304050608 >> 56;
                 *
                 * Doing it like this avoids warnings on 32-bit machines.
                 */
                long a = (REPEAT_BYTE(0x01) / 0xff + 1);
                return mask * a >> (sizeof(long) * 7);
        } else {
                /* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
                /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
                long a = (0x0ff0001 + mask) >> 23;
                /* Fix the 1 for 00 case */
                return a & mask;
        }
}

unsigned long xdl_hash_record(char const **data, char const *top, long flags)
{
        unsigned long hash = 5381;
        unsigned long a = 0, mask = 0;
        char const *ptr = *data;
        char const *end = top - sizeof(unsigned long) + 1;

        if (flags & XDF_WHITESPACE_FLAGS)
                return xdl_hash_record_with_whitespace(data, top, flags);

        ptr -= sizeof(unsigned long);
        do {
                hash += hash << 5;
                hash ^= a;
                ptr += sizeof(unsigned long);
                if (ptr >= end)
                        break;
                a = *(unsigned long *)ptr;
                /* Do we have any '\n' bytes in this word? */
                mask = has_zero(a ^ NEWLINEBYTES);
        } while (!mask);

        if (ptr >= end) {
                /*
                 * There is only a partial word left at the end of the
                 * buffer. Because we may work with a memory mapping,
                 * we have to grab the rest byte by byte instead of
                 * blindly reading it.
                 *
                 * To avoid problems with masking in a signed value,
                 * we use an unsigned char here.
                 */
                const char *p;
                for (p = top - 1; p >= ptr; p--)
                        a = (a << 8) + *((const unsigned char *)p);
                mask = has_zero(a ^ NEWLINEBYTES);
                if (!mask)
                        /*
                         * No '\n' found in the partial word.  Make a
                         * mask that matches what we read.
                         */
                        mask = 1UL << (8 * (top - ptr) + 7);
        }

        /* The mask *below* the first high bit set */
        mask = (mask - 1) & ~mask;
        mask >>= 7;
        hash += hash << 5;
        hash ^= a & mask;

        /* Advance past the last (possibly partial) word */
        ptr += count_masked_bytes(mask);

        if (ptr < top) {
                assert(*ptr == '\n');
                ptr++;
        }

        *data = ptr;

        return hash;
}

#else /* XDL_FAST_HASH */

unsigned long xdl_hash_record(char const **data, char const *top, long flags) {
        unsigned long ha = 5381;
        char const *ptr = *data;

        if (flags & XDF_WHITESPACE_FLAGS)
                return xdl_hash_record_with_whitespace(data, top, flags);

        for (; ptr < top && *ptr != '\n'; ptr++) {
                ha += (ha << 5);
                ha ^= (unsigned long) *ptr;
        }
        *data = ptr < top ? ptr + 1: ptr;

        return ha;
}

#endif /* XDL_FAST_HASH */

unsigned int xdl_hashbits(unsigned int size) {
        unsigned int val = 1, bits = 0;

        for (; val < size && bits < CHAR_BIT * sizeof(unsigned int); val <<= 1, bits++);
        return bits ? bits: 1;
}


int xdl_num_out(char *out, long val) {
        char *ptr, *str = out;
        char buf[32];

        ptr = buf + sizeof(buf) - 1;
        *ptr = '\0';
        if (val < 0) {
                *--ptr = '-';
                val = -val;
        }
        for (; val && ptr > buf; val /= 10)
                *--ptr = "0123456789"[val % 10];
        if (*ptr)
                for (; *ptr; ptr++, str++)
                        *str = *ptr;
        else
                *str++ = '0';
        *str = '\0';

        return str - out;
}

int xdl_emit_hunk_hdr(long s1, long c1, long s2, long c2,
                      const char *func, long funclen, xdemitcb_t *ecb) {
        int nb = 0;
        mmbuffer_t mb;
        char buf[128];

        memcpy(buf, "@@ -", 4);
        nb += 4;

        nb += xdl_num_out(buf + nb, c1 ? s1: s1 - 1);

        if (c1 != 1) {
                memcpy(buf + nb, ",", 1);
                nb += 1;

                nb += xdl_num_out(buf + nb, c1);
        }

        memcpy(buf + nb, " +", 2);
        nb += 2;

        nb += xdl_num_out(buf + nb, c2 ? s2: s2 - 1);

        if (c2 != 1) {
                memcpy(buf + nb, ",", 1);
                nb += 1;

                nb += xdl_num_out(buf + nb, c2);
        }

        memcpy(buf + nb, " @@", 3);
        nb += 3;
        if (func && funclen) {
                buf[nb++] = ' ';
                if (funclen > sizeof(buf) - nb - 1)
                        funclen = sizeof(buf) - nb - 1;
                memcpy(buf + nb, func, funclen);
                nb += funclen;
        }
        buf[nb++] = '\n';

        mb.ptr = buf;
        mb.size = nb;
        if (ecb->outf(ecb->priv, &mb, 1) < 0)
                return -1;

        return 0;
}

int xdl_fall_back_diff(xdfenv_t *diff_env, xpparam_t const *xpp,
                int line1, int count1, int line2, int count2)
{
        /*
         * This probably does not work outside Git, since
         * we have a very simple mmfile structure.
         *
         * Note: ideally, we would reuse the prepared environment, but
         * the libxdiff interface does not (yet) allow for diffing only
         * ranges of lines instead of the whole files.
         */
        mmfile_t subfile1, subfile2;
        xdfenv_t env;

        subfile1.ptr = (char *)diff_env->xdf1.recs[line1 - 1]->ptr;
        subfile1.size = diff_env->xdf1.recs[line1 + count1 - 2]->ptr +
                diff_env->xdf1.recs[line1 + count1 - 2]->size - subfile1.ptr;
        subfile2.ptr = (char *)diff_env->xdf2.recs[line2 - 1]->ptr;
        subfile2.size = diff_env->xdf2.recs[line2 + count2 - 2]->ptr +
                diff_env->xdf2.recs[line2 + count2 - 2]->size - subfile2.ptr;
        if (xdl_do_diff(&subfile1, &subfile2, xpp, &env) < 0)
                return -1;

        memcpy(diff_env->xdf1.rchg + line1 - 1, env.xdf1.rchg, count1);
        memcpy(diff_env->xdf2.rchg + line2 - 1, env.xdf2.rchg, count2);

        xdl_free_env(&env);

        return 0;
}