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-rw-r--r--chunk-format.c179
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;
+}