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125 lines
4.1 KiB
C
125 lines
4.1 KiB
C
///////////////////////////////////////////////////////////////////////////////
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//
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/// \file file_io.h
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/// \brief I/O types and functions
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//
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// Author: Lasse Collin
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//
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// This file has been put into the public domain.
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// You can do whatever you want with this file.
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//
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///////////////////////////////////////////////////////////////////////////////
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// Some systems have suboptimal BUFSIZ. Use a bit bigger value on them.
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// We also need that IO_BUFFER_SIZE is a multiple of 8 (sizeof(uint64_t))
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#if BUFSIZ <= 1024
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# define IO_BUFFER_SIZE 8192
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#else
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# define IO_BUFFER_SIZE (BUFSIZ & ~7U)
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#endif
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/// is_sparse() accesses the buffer as uint64_t for maximum speed.
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/// Use an union to make sure that the buffer is properly aligned.
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typedef union {
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uint8_t u8[IO_BUFFER_SIZE];
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uint32_t u32[IO_BUFFER_SIZE / sizeof(uint32_t)];
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uint64_t u64[IO_BUFFER_SIZE / sizeof(uint64_t)];
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} io_buf;
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typedef struct {
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/// Name of the source filename (as given on the command line) or
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/// pointer to static "(stdin)" when reading from standard input.
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const char *src_name;
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/// Destination filename converted from src_name or pointer to static
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/// "(stdout)" when writing to standard output.
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char *dest_name;
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/// File descriptor of the source file
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int src_fd;
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/// File descriptor of the target file
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int dest_fd;
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/// True once end of the source file has been detected.
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bool src_eof;
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/// If true, we look for long chunks of zeros and try to create
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/// a sparse file.
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bool dest_try_sparse;
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/// This is used only if dest_try_sparse is true. This holds the
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/// number of zero bytes we haven't written out, because we plan
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/// to make that byte range a sparse chunk.
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off_t dest_pending_sparse;
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/// Stat of the source file.
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struct stat src_st;
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/// Stat of the destination file.
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struct stat dest_st;
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} file_pair;
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/// \brief Initialize the I/O module
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extern void io_init(void);
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/// \brief Disable creation of sparse files when decompressing
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extern void io_no_sparse(void);
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/// \brief Opens a file pair
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extern file_pair *io_open(const char *src_name);
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/// \brief Closes the file descriptors and frees possible allocated memory
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///
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/// The success argument determines if source or destination file gets
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/// unlinked:
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/// - false: The destination file is unlinked.
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/// - true: The source file is unlinked unless writing to stdout or --keep
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/// was used.
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extern void io_close(file_pair *pair, bool success);
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/// \brief Reads from the source file to a buffer
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///
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/// \param pair File pair having the source file open for reading
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/// \param buf Destination buffer to hold the read data
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/// \param size Size of the buffer; assumed be smaller than SSIZE_MAX
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///
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/// \return On success, number of bytes read is returned. On end of
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/// file zero is returned and pair->src_eof set to true.
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/// On error, SIZE_MAX is returned and error message printed.
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extern size_t io_read(file_pair *pair, io_buf *buf, size_t size);
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/// \brief Read from source file from given offset to a buffer
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///
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/// This is remotely similar to standard pread(). This uses lseek() though,
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/// so the read offset is changed on each call.
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///
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/// \param pair Seekable source file
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/// \param buf Destination buffer
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/// \param size Amount of data to read
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/// \param pos Offset relative to the beginning of the file,
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/// from which the data should be read.
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///
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/// \return On success, false is returned. On error, error message
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/// is printed and true is returned.
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extern bool io_pread(file_pair *pair, io_buf *buf, size_t size, off_t pos);
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/// \brief Writes a buffer to the destination file
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///
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/// \param pair File pair having the destination file open for writing
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/// \param buf Buffer containing the data to be written
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/// \param size Size of the buffer; assumed be smaller than SSIZE_MAX
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///
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/// \return On success, zero is returned. On error, -1 is returned
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/// and error message printed.
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extern bool io_write(file_pair *pair, const io_buf *buf, size_t size);
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