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5f0879f54b
Add the capability to read the table of contents, then pair the chunks
with necessary logic using read_chunk_fn pointers. Callers will be added
in future changes, but the typical outline will be:
1. initialize a 'struct chunkfile' with init_chunkfile(NULL).
2. call read_table_of_contents().
3. for each chunk to parse,
a. call pair_chunk() to assign a pointer with the chunk position, or
b. call read_chunk() to run a callback on the chunk start and size.
4. call free_chunkfile() to clear the 'struct chunkfile' data.
We are re-using the anonymous 'struct chunkfile' data, as it is internal
to the chunk-format API. This gives it essentially two modes: write and
read. If the same struct instance was used for both reads and writes,
then there would be failures.
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
68 lines
1.9 KiB
C
68 lines
1.9 KiB
C
#ifndef CHUNK_FORMAT_H
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#define CHUNK_FORMAT_H
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#include "git-compat-util.h"
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struct hashfile;
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struct chunkfile;
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#define CHUNK_TOC_ENTRY_SIZE (sizeof(uint32_t) + sizeof(uint64_t))
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/*
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* Initialize a 'struct chunkfile' for writing _or_ reading a file
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* with the chunk format.
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*
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* If writing a file, supply a non-NULL 'struct hashfile *' that will
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* be used to write.
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*
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* If reading a file, use a NULL 'struct hashfile *' and then call
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* read_table_of_contents(). Supply the memory-mapped data to the
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* pair_chunk() or read_chunk() methods, as appropriate.
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*
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* DO NOT MIX THESE MODES. Use different 'struct chunkfile' instances
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* for reading and writing.
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*/
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struct chunkfile *init_chunkfile(struct hashfile *f);
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void free_chunkfile(struct chunkfile *cf);
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int get_num_chunks(struct chunkfile *cf);
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typedef int (*chunk_write_fn)(struct hashfile *f, void *data);
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void add_chunk(struct chunkfile *cf,
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uint32_t id,
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size_t size,
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chunk_write_fn fn);
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int write_chunkfile(struct chunkfile *cf, void *data);
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int read_table_of_contents(struct chunkfile *cf,
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const unsigned char *mfile,
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size_t mfile_size,
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uint64_t toc_offset,
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int toc_length);
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#define CHUNK_NOT_FOUND (-2)
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/*
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* Find 'chunk_id' in the given chunkfile and assign the
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* given pointer to the position in the mmap'd file where
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* that chunk begins.
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*
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* Returns CHUNK_NOT_FOUND if the chunk does not exist.
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*/
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int pair_chunk(struct chunkfile *cf,
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uint32_t chunk_id,
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const unsigned char **p);
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typedef int (*chunk_read_fn)(const unsigned char *chunk_start,
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size_t chunk_size, void *data);
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/*
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* Find 'chunk_id' in the given chunkfile and call the
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* given chunk_read_fn method with the information for
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* that chunk.
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*
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* Returns CHUNK_NOT_FOUND if the chunk does not exist.
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*/
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int read_chunk(struct chunkfile *cf,
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uint32_t chunk_id,
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chunk_read_fn fn,
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void *data);
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#endif
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