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953d2001fa
The new read_trailing_table_of_contents() mimics read_table_of_contents() except that it reads the table of contents in reverse from the end of the given hashfile. The file is given as a memory-mapped section of memory and a size. Automatically calculate the start of the trailing hash and read the table of contents in revers from that position. The errors come along from those in read_table_of_contents(). The one exception is that the chunk_offset cannot be checked as going into the table of contents since we do not have that length automatically. That may have some surprising results for some narrow forms of corruption. However, we do still limit the size to the size of the file plus the part of the table of contents read so far. At minimum, the given sizes can be used to limit parsing within the file itself. Signed-off-by: Derrick Stolee <derrickstolee@github.com> Signed-off-by: Taylor Blau <me@ttaylorr.com>
88 lines
2.4 KiB
C
88 lines
2.4 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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#include "hash.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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enum chunkfile_flags {
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CHUNKFILE_TRAILING_TOC = (1 << 0),
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};
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int write_chunkfile(struct chunkfile *cf,
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enum chunkfile_flags flags,
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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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/**
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* Read the given chunkfile, but read the table of contents from the
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* end of the given mfile. The file is expected to be a hashfile with
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* the_hash_file->rawsz bytes at the end storing the hash.
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*/
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int read_trailing_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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#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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uint8_t oid_version(const struct git_hash_algo *algop);
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#endif
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