diff options
Diffstat (limited to 'chunk-format.c')
| -rw-r--r-- | chunk-format.c | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/chunk-format.c b/chunk-format.c new file mode 100644 index 0000000000..da191e59a2 --- /dev/null +++ b/chunk-format.c @@ -0,0 +1,179 @@ +#include "cache.h" +#include "chunk-format.h" +#include "csum-file.h" + +/* + * When writing a chunk-based file format, collect the chunks in + * an array of chunk_info structs. The size stores the _expected_ + * amount of data that will be written by write_fn. + */ +struct chunk_info { + uint32_t id; + uint64_t size; + chunk_write_fn write_fn; + + const void *start; +}; + +struct chunkfile { + struct hashfile *f; + + struct chunk_info *chunks; + size_t chunks_nr; + size_t chunks_alloc; +}; + +struct chunkfile *init_chunkfile(struct hashfile *f) +{ + struct chunkfile *cf = xcalloc(1, sizeof(*cf)); + cf->f = f; + return cf; +} + +void free_chunkfile(struct chunkfile *cf) +{ + if (!cf) + return; + free(cf->chunks); + free(cf); +} + +int get_num_chunks(struct chunkfile *cf) +{ + return cf->chunks_nr; +} + +void add_chunk(struct chunkfile *cf, + uint32_t id, + size_t size, + chunk_write_fn fn) +{ + ALLOC_GROW(cf->chunks, cf->chunks_nr + 1, cf->chunks_alloc); + + cf->chunks[cf->chunks_nr].id = id; + cf->chunks[cf->chunks_nr].write_fn = fn; + cf->chunks[cf->chunks_nr].size = size; + cf->chunks_nr++; +} + +int write_chunkfile(struct chunkfile *cf, void *data) +{ + int i; + uint64_t cur_offset = hashfile_total(cf->f); + + /* Add the table of contents to the current offset */ + cur_offset += (cf->chunks_nr + 1) * CHUNK_TOC_ENTRY_SIZE; + + for (i = 0; i < cf->chunks_nr; i++) { + hashwrite_be32(cf->f, cf->chunks[i].id); + hashwrite_be64(cf->f, cur_offset); + + cur_offset += cf->chunks[i].size; + } + + /* Trailing entry marks the end of the chunks */ + hashwrite_be32(cf->f, 0); + hashwrite_be64(cf->f, cur_offset); + + for (i = 0; i < cf->chunks_nr; i++) { + off_t start_offset = hashfile_total(cf->f); + int result = cf->chunks[i].write_fn(cf->f, data); + + if (result) + return result; + + if (hashfile_total(cf->f) - start_offset != cf->chunks[i].size) + BUG("expected to write %"PRId64" bytes to chunk %"PRIx32", but wrote %"PRId64" instead", + cf->chunks[i].size, cf->chunks[i].id, + hashfile_total(cf->f) - start_offset); + } + + return 0; +} + +int read_table_of_contents(struct chunkfile *cf, + const unsigned char *mfile, + size_t mfile_size, + uint64_t toc_offset, + int toc_length) +{ + int i; + uint32_t chunk_id; + const unsigned char *table_of_contents = mfile + toc_offset; + + ALLOC_GROW(cf->chunks, toc_length, cf->chunks_alloc); + + while (toc_length--) { + uint64_t chunk_offset, next_chunk_offset; + + chunk_id = get_be32(table_of_contents); + chunk_offset = get_be64(table_of_contents + 4); + + if (!chunk_id) { + error(_("terminating chunk id appears earlier than expected")); + return 1; + } + + table_of_contents += CHUNK_TOC_ENTRY_SIZE; + next_chunk_offset = get_be64(table_of_contents + 4); + + if (next_chunk_offset < chunk_offset || + next_chunk_offset > mfile_size - the_hash_algo->rawsz) { + error(_("improper chunk offset(s) %"PRIx64" and %"PRIx64""), + chunk_offset, next_chunk_offset); + return -1; + } + + for (i = 0; i < cf->chunks_nr; i++) { + if (cf->chunks[i].id == chunk_id) { + error(_("duplicate chunk ID %"PRIx32" found"), + chunk_id); + return -1; + } + } + + cf->chunks[cf->chunks_nr].id = chunk_id; + cf->chunks[cf->chunks_nr].start = mfile + chunk_offset; + cf->chunks[cf->chunks_nr].size = next_chunk_offset - chunk_offset; + cf->chunks_nr++; + } + + chunk_id = get_be32(table_of_contents); + if (chunk_id) { + error(_("final chunk has non-zero id %"PRIx32""), chunk_id); + return -1; + } + + return 0; +} + +static int pair_chunk_fn(const unsigned char *chunk_start, + size_t chunk_size, + void *data) +{ + const unsigned char **p = data; + *p = chunk_start; + return 0; +} + +int pair_chunk(struct chunkfile *cf, + uint32_t chunk_id, + const unsigned char **p) +{ + return read_chunk(cf, chunk_id, pair_chunk_fn, p); +} + +int read_chunk(struct chunkfile *cf, + uint32_t chunk_id, + chunk_read_fn fn, + void *data) +{ + int i; + + for (i = 0; i < cf->chunks_nr; i++) { + if (cf->chunks[i].id == chunk_id) + return fn(cf->chunks[i].start, cf->chunks[i].size, data); + } + + return CHUNK_NOT_FOUND; +} |