Merge branch 'rs/nth-switch-code-simplification'
[git/git.git] / vcs-svn / svndiff.c
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
47 struct 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
56 static void window_release(struct window *ctx)
57 {
58 strbuf_release(&ctx->out);
59 strbuf_release(&ctx->instructions);
60 strbuf_release(&ctx->data);
61 }
62
63 static 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_errno("cannot write delta postimage");
68 }
69
70 static int error_short_read(struct line_buffer *input)
71 {
72 if (buffer_ferror(input))
73 return error_errno("error reading delta");
74 return error("invalid delta: unexpected end of file");
75 }
76
77 static int read_chunk(struct line_buffer *delta, off_t *delta_len,
78 struct strbuf *buf, size_t len)
79 {
80 assert(*delta_len >= 0);
81 strbuf_reset(buf);
82 if (len > (uintmax_t) *delta_len ||
83 buffer_read_binary(delta, buf, len) != len)
84 return error_short_read(delta);
85 *delta_len -= buf->len;
86 return 0;
87 }
88
89 static int read_magic(struct line_buffer *in, off_t *len)
90 {
91 static const char magic[] = {'S', 'V', 'N', '\0'};
92 struct strbuf sb = STRBUF_INIT;
93
94 if (read_chunk(in, len, &sb, sizeof(magic))) {
95 strbuf_release(&sb);
96 return -1;
97 }
98 if (memcmp(sb.buf, magic, sizeof(magic))) {
99 strbuf_release(&sb);
100 return error("invalid delta: unrecognized file type");
101 }
102 strbuf_release(&sb);
103 return 0;
104 }
105
106 static int read_int(struct line_buffer *in, uintmax_t *result, off_t *len)
107 {
108 uintmax_t rv = 0;
109 off_t sz;
110 for (sz = *len; sz; sz--) {
111 const int ch = buffer_read_char(in);
112 if (ch == EOF)
113 break;
114
115 rv <<= VLI_BITS_PER_DIGIT;
116 rv += (ch & VLI_DIGIT_MASK);
117 if (ch & VLI_CONTINUE)
118 continue;
119
120 *result = rv;
121 *len = sz - 1;
122 return 0;
123 }
124 return error_short_read(in);
125 }
126
127 static int parse_int(const char **buf, size_t *result, const char *end)
128 {
129 size_t rv = 0;
130 const char *pos;
131 for (pos = *buf; pos != end; pos++) {
132 unsigned char ch = *pos;
133
134 rv <<= VLI_BITS_PER_DIGIT;
135 rv += (ch & VLI_DIGIT_MASK);
136 if (ch & VLI_CONTINUE)
137 continue;
138
139 *result = rv;
140 *buf = pos + 1;
141 return 0;
142 }
143 return error("invalid delta: unexpected end of instructions section");
144 }
145
146 static int read_offset(struct line_buffer *in, off_t *result, off_t *len)
147 {
148 uintmax_t val;
149 if (read_int(in, &val, len))
150 return -1;
151 if (val > maximum_signed_value_of_type(off_t))
152 return error("unrepresentable offset in delta: %"PRIuMAX"", val);
153 *result = val;
154 return 0;
155 }
156
157 static int read_length(struct line_buffer *in, size_t *result, off_t *len)
158 {
159 uintmax_t val;
160 if (read_int(in, &val, len))
161 return -1;
162 if (val > SIZE_MAX)
163 return error("unrepresentable length in delta: %"PRIuMAX"", val);
164 *result = val;
165 return 0;
166 }
167
168 static int copyfrom_source(struct window *ctx, const char **instructions,
169 size_t nbytes, const char *insns_end)
170 {
171 size_t offset;
172 if (parse_int(instructions, &offset, insns_end))
173 return -1;
174 if (unsigned_add_overflows(offset, nbytes) ||
175 offset + nbytes > ctx->in->width)
176 return error("invalid delta: copies source data outside view");
177 strbuf_add(&ctx->out, ctx->in->buf.buf + offset, nbytes);
178 return 0;
179 }
180
181 static int copyfrom_target(struct window *ctx, const char **instructions,
182 size_t nbytes, const char *instructions_end)
183 {
184 size_t offset;
185 if (parse_int(instructions, &offset, instructions_end))
186 return -1;
187 if (offset >= ctx->out.len)
188 return error("invalid delta: copies from the future");
189 for (; nbytes > 0; nbytes--)
190 strbuf_addch(&ctx->out, ctx->out.buf[offset++]);
191 return 0;
192 }
193
194 static int copyfrom_data(struct window *ctx, size_t *data_pos, size_t nbytes)
195 {
196 const size_t pos = *data_pos;
197 if (unsigned_add_overflows(pos, nbytes) ||
198 pos + nbytes > ctx->data.len)
199 return error("invalid delta: copies unavailable inline data");
200 strbuf_add(&ctx->out, ctx->data.buf + pos, nbytes);
201 *data_pos += nbytes;
202 return 0;
203 }
204
205 static int parse_first_operand(const char **buf, size_t *out, const char *end)
206 {
207 size_t result = (unsigned char) *(*buf)++ & OPERAND_MASK;
208 if (result) { /* immediate operand */
209 *out = result;
210 return 0;
211 }
212 return parse_int(buf, out, end);
213 }
214
215 static int execute_one_instruction(struct window *ctx,
216 const char **instructions, size_t *data_pos)
217 {
218 unsigned int instruction;
219 const char *insns_end = ctx->instructions.buf + ctx->instructions.len;
220 size_t nbytes;
221 assert(ctx);
222 assert(instructions && *instructions);
223 assert(data_pos);
224
225 instruction = (unsigned char) **instructions;
226 if (parse_first_operand(instructions, &nbytes, insns_end))
227 return -1;
228 switch (instruction & INSN_MASK) {
229 case INSN_COPYFROM_SOURCE:
230 return copyfrom_source(ctx, instructions, nbytes, insns_end);
231 case INSN_COPYFROM_TARGET:
232 return copyfrom_target(ctx, instructions, nbytes, insns_end);
233 case INSN_COPYFROM_DATA:
234 return copyfrom_data(ctx, data_pos, nbytes);
235 default:
236 return error("invalid delta: unrecognized instruction");
237 }
238 }
239
240 static int apply_window_in_core(struct window *ctx)
241 {
242 const char *instructions;
243 size_t data_pos = 0;
244
245 /*
246 * Fill ctx->out.buf using data from the source, target,
247 * and inline data views.
248 */
249 for (instructions = ctx->instructions.buf;
250 instructions != ctx->instructions.buf + ctx->instructions.len;
251 )
252 if (execute_one_instruction(ctx, &instructions, &data_pos))
253 return -1;
254 if (data_pos != ctx->data.len)
255 return error("invalid delta: does not copy all inline data");
256 return 0;
257 }
258
259 static int apply_one_window(struct line_buffer *delta, off_t *delta_len,
260 struct sliding_view *preimage, FILE *out)
261 {
262 int rv = -1;
263 struct window ctx = WINDOW_INIT(preimage);
264 size_t out_len;
265 size_t instructions_len;
266 size_t data_len;
267 assert(delta_len);
268
269 /* "source view" offset and length already handled; */
270 if (read_length(delta, &out_len, delta_len) ||
271 read_length(delta, &instructions_len, delta_len) ||
272 read_length(delta, &data_len, delta_len) ||
273 read_chunk(delta, delta_len, &ctx.instructions, instructions_len) ||
274 read_chunk(delta, delta_len, &ctx.data, data_len))
275 goto error_out;
276 strbuf_grow(&ctx.out, out_len);
277 if (apply_window_in_core(&ctx))
278 goto error_out;
279 if (ctx.out.len != out_len) {
280 rv = error("invalid delta: incorrect postimage length");
281 goto error_out;
282 }
283 if (write_strbuf(&ctx.out, out))
284 goto error_out;
285 rv = 0;
286 error_out:
287 window_release(&ctx);
288 return rv;
289 }
290
291 int svndiff0_apply(struct line_buffer *delta, off_t delta_len,
292 struct sliding_view *preimage, FILE *postimage)
293 {
294 assert(delta && preimage && postimage && delta_len >= 0);
295
296 if (read_magic(delta, &delta_len))
297 return -1;
298 while (delta_len) { /* For each window: */
299 off_t pre_off = -1;
300 size_t pre_len;
301
302 if (read_offset(delta, &pre_off, &delta_len) ||
303 read_length(delta, &pre_len, &delta_len) ||
304 move_window(preimage, pre_off, pre_len) ||
305 apply_one_window(delta, &delta_len, preimage, postimage))
306 return -1;
307 }
308 return 0;
309 }