Andrew's git - gitweb.git/blob

   1/*
   2 * Licensed under a two-clause BSD-style license.
   3 * See LICENSE for details.
   4 */
   5
   6#include "git-compat-util.h"
   7#include "sliding_window.h"
   8#include "line_buffer.h"
   9#include "svndiff.h"
  10
  11/*
  12 * svndiff0 applier
  13 *
  14 * See http://svn.apache.org/repos/asf/subversion/trunk/notes/svndiff.
  15 *
  16 * svndiff0 ::= 'SVN\0' window*
  17 * window ::= int int int int int instructions inline_data;
  18 * instructions ::= instruction*;
  19 * instruction ::= view_selector int int
  20 *   | copyfrom_data int
  21 *   | packed_view_selector int
  22 *   | packed_copyfrom_data
  23 *   ;
  24 * view_selector ::= copyfrom_source
  25 *   | copyfrom_target
  26 *   ;
  27 * copyfrom_source ::= # binary 00 000000;
  28 * copyfrom_target ::= # binary 01 000000;
  29 * copyfrom_data ::= # binary 10 000000;
  30 * packed_view_selector ::= # view_selector OR-ed with 6 bit value;
  31 * packed_copyfrom_data ::= # copyfrom_data OR-ed with 6 bit value;
  32 * int ::= highdigit* lowdigit;
  33 * highdigit ::= # binary 1000 0000 OR-ed with 7 bit value;
  34 * lowdigit ::= # 7 bit value;
  35 */
  36
  37#define INSN_MASK       0xc0
  38#define INSN_COPYFROM_SOURCE    0x00
  39#define INSN_COPYFROM_TARGET    0x40
  40#define INSN_COPYFROM_DATA      0x80
  41#define OPERAND_MASK    0x3f
  42
  43#define VLI_CONTINUE    0x80
  44#define VLI_DIGIT_MASK  0x7f
  45#define VLI_BITS_PER_DIGIT 7
  46
  47struct window {
  48        struct sliding_view *in;
  49        struct strbuf out;
  50        struct strbuf instructions;
  51        struct strbuf data;
  52};
  53
  54#define WINDOW_INIT(w)  { (w), STRBUF_INIT, STRBUF_INIT, STRBUF_INIT }
  55
  56static void window_release(struct window *ctx)
  57{
  58        strbuf_release(&ctx->out);
  59        strbuf_release(&ctx->instructions);
  60        strbuf_release(&ctx->data);
  61}
  62
  63static int write_strbuf(struct strbuf *sb, FILE *out)
  64{
  65        if (fwrite(sb->buf, 1, sb->len, out) == sb->len)        /* Success. */
  66                return 0;
  67        return error("cannot write delta postimage: %s", strerror(errno));
  68}
  69
  70static int error_short_read(struct line_buffer *input)
  71{
  72        if (buffer_ferror(input))
  73                return error("error reading delta: %s", strerror(errno));
  74        return error("invalid delta: unexpected end of file");
  75}
  76
  77static int read_chunk(struct line_buffer *delta, off_t *delta_len,
  78                      struct strbuf *buf, size_t len)
  79{
  80        strbuf_reset(buf);
  81        if (len > *delta_len ||
  82            buffer_read_binary(delta, buf, len) != len)
  83                return error_short_read(delta);
  84        *delta_len -= buf->len;
  85        return 0;
  86}
  87
  88static int read_magic(struct line_buffer *in, off_t *len)
  89{
  90        static const char magic[] = {'S', 'V', 'N', '\0'};
  91        struct strbuf sb = STRBUF_INIT;
  92
  93        if (read_chunk(in, len, &sb, sizeof(magic))) {
  94                strbuf_release(&sb);
  95                return -1;
  96        }
  97        if (memcmp(sb.buf, magic, sizeof(magic))) {
  98                strbuf_release(&sb);
  99                return error("invalid delta: unrecognized file type");
 100        }
 101        strbuf_release(&sb);
 102        return 0;
 103}
 104
 105static int read_int(struct line_buffer *in, uintmax_t *result, off_t *len)
 106{
 107        uintmax_t rv = 0;
 108        off_t sz;
 109        for (sz = *len; sz; sz--) {
 110                const int ch = buffer_read_char(in);
 111                if (ch == EOF)
 112                        break;
 113
 114                rv <<= VLI_BITS_PER_DIGIT;
 115                rv += (ch & VLI_DIGIT_MASK);
 116                if (ch & VLI_CONTINUE)
 117                        continue;
 118
 119                *result = rv;
 120                *len = sz - 1;
 121                return 0;
 122        }
 123        return error_short_read(in);
 124}
 125
 126static int parse_int(const char **buf, size_t *result, const char *end)
 127{
 128        size_t rv = 0;
 129        const char *pos;
 130        for (pos = *buf; pos != end; pos++) {
 131                unsigned char ch = *pos;
 132
 133                rv <<= VLI_BITS_PER_DIGIT;
 134                rv += (ch & VLI_DIGIT_MASK);
 135                if (ch & VLI_CONTINUE)
 136                        continue;
 137
 138                *result = rv;
 139                *buf = pos + 1;
 140                return 0;
 141        }
 142        return error("invalid delta: unexpected end of instructions section");
 143}
 144
 145static int read_offset(struct line_buffer *in, off_t *result, off_t *len)
 146{
 147        uintmax_t val;
 148        if (read_int(in, &val, len))
 149                return -1;
 150        if (val > maximum_signed_value_of_type(off_t))
 151                return error("unrepresentable offset in delta: %"PRIuMAX"", val);
 152        *result = val;
 153        return 0;
 154}
 155
 156static int read_length(struct line_buffer *in, size_t *result, off_t *len)
 157{
 158        uintmax_t val;
 159        if (read_int(in, &val, len))
 160                return -1;
 161        if (val > SIZE_MAX)
 162                return error("unrepresentable length in delta: %"PRIuMAX"", val);
 163        *result = val;
 164        return 0;
 165}
 166
 167static int copyfrom_source(struct window *ctx, const char **instructions,
 168                           size_t nbytes, const char *insns_end)
 169{
 170        size_t offset;
 171        if (parse_int(instructions, &offset, insns_end))
 172                return -1;
 173        if (unsigned_add_overflows(offset, nbytes) ||
 174            offset + nbytes > ctx->in->width)
 175                return error("invalid delta: copies source data outside view");
 176        strbuf_add(&ctx->out, ctx->in->buf.buf + offset, nbytes);
 177        return 0;
 178}
 179
 180static int copyfrom_target(struct window *ctx, const char **instructions,
 181                           size_t nbytes, const char *instructions_end)
 182{
 183        size_t offset;
 184        if (parse_int(instructions, &offset, instructions_end))
 185                return -1;
 186        if (offset >= ctx->out.len)
 187                return error("invalid delta: copies from the future");
 188        for (; nbytes > 0; nbytes--)
 189                strbuf_addch(&ctx->out, ctx->out.buf[offset++]);
 190        return 0;
 191}
 192
 193static int copyfrom_data(struct window *ctx, size_t *data_pos, size_t nbytes)
 194{
 195        const size_t pos = *data_pos;
 196        if (unsigned_add_overflows(pos, nbytes) ||
 197            pos + nbytes > ctx->data.len)
 198                return error("invalid delta: copies unavailable inline data");
 199        strbuf_add(&ctx->out, ctx->data.buf + pos, nbytes);
 200        *data_pos += nbytes;
 201        return 0;
 202}
 203
 204static int parse_first_operand(const char **buf, size_t *out, const char *end)
 205{
 206        size_t result = (unsigned char) *(*buf)++ & OPERAND_MASK;
 207        if (result) {   /* immediate operand */
 208                *out = result;
 209                return 0;
 210        }
 211        return parse_int(buf, out, end);
 212}
 213
 214static int execute_one_instruction(struct window *ctx,
 215                                const char **instructions, size_t *data_pos)
 216{
 217        unsigned int instruction;
 218        const char *insns_end = ctx->instructions.buf + ctx->instructions.len;
 219        size_t nbytes;
 220        assert(ctx);
 221        assert(instructions && *instructions);
 222        assert(data_pos);
 223
 224        instruction = (unsigned char) **instructions;
 225        if (parse_first_operand(instructions, &nbytes, insns_end))
 226                return -1;
 227        switch (instruction & INSN_MASK) {
 228        case INSN_COPYFROM_SOURCE:
 229                return copyfrom_source(ctx, instructions, nbytes, insns_end);
 230        case INSN_COPYFROM_TARGET:
 231                return copyfrom_target(ctx, instructions, nbytes, insns_end);
 232        case INSN_COPYFROM_DATA:
 233                return copyfrom_data(ctx, data_pos, nbytes);
 234        default:
 235                return error("invalid delta: unrecognized instruction");
 236        }
 237}
 238
 239static int apply_window_in_core(struct window *ctx)
 240{
 241        const char *instructions;
 242        size_t data_pos = 0;
 243
 244        /*
 245         * Fill ctx->out.buf using data from the source, target,
 246         * and inline data views.
 247         */
 248        for (instructions = ctx->instructions.buf;
 249             instructions != ctx->instructions.buf + ctx->instructions.len;
 250             )
 251                if (execute_one_instruction(ctx, &instructions, &data_pos))
 252                        return -1;
 253        if (data_pos != ctx->data.len)
 254                return error("invalid delta: does not copy all inline data");
 255        return 0;
 256}
 257
 258static int apply_one_window(struct line_buffer *delta, off_t *delta_len,
 259                            struct sliding_view *preimage, FILE *out)
 260{
 261        struct window ctx = WINDOW_INIT(preimage);
 262        size_t out_len;
 263        size_t instructions_len;
 264        size_t data_len;
 265        assert(delta_len);
 266
 267        /* "source view" offset and length already handled; */
 268        if (read_length(delta, &out_len, delta_len) ||
 269            read_length(delta, &instructions_len, delta_len) ||
 270            read_length(delta, &data_len, delta_len) ||
 271            read_chunk(delta, delta_len, &ctx.instructions, instructions_len) ||
 272            read_chunk(delta, delta_len, &ctx.data, data_len))
 273                goto error_out;
 274        strbuf_grow(&ctx.out, out_len);
 275        if (apply_window_in_core(&ctx))
 276                goto error_out;
 277        if (ctx.out.len != out_len) {
 278                error("invalid delta: incorrect postimage length");
 279                goto error_out;
 280        }
 281        if (write_strbuf(&ctx.out, out))
 282                goto error_out;
 283        window_release(&ctx);
 284        return 0;
 285error_out:
 286        window_release(&ctx);
 287        return -1;
 288}
 289
 290int svndiff0_apply(struct line_buffer *delta, off_t delta_len,
 291                        struct sliding_view *preimage, FILE *postimage)
 292{
 293        assert(delta && preimage && postimage);
 294
 295        if (read_magic(delta, &delta_len))
 296                return -1;
 297        while (delta_len) {     /* For each window: */
 298                off_t pre_off = pre_off; /* stupid GCC... */
 299                size_t pre_len;
 300
 301                if (read_offset(delta, &pre_off, &delta_len) ||
 302                    read_length(delta, &pre_len, &delta_len) ||
 303                    move_window(preimage, pre_off, pre_len) ||
 304                    apply_one_window(delta, &delta_len, preimage, postimage))
 305                        return -1;
 306        }
 307        return 0;
 308}