The second batch

[git] / chunk-format.c

#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, result = 0;
        uint64_t cur_offset = hashfile_total(cf->f);

        trace2_region_enter("chunkfile", "write", the_repository);

        /* 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);
                result = cf->chunks[i].write_fn(cf->f, data);

                if (result)
                        goto cleanup;

                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);
        }

cleanup:
        trace2_region_leave("chunkfile", "write", the_repository);
        return result;
}

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;
}