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/* libhw/generic/io.h - Device-independent I/O definitions
*
* Copyright (C) 2024-2025 Luke T. Shumaker <lukeshu@lukeshu.com>
* SPDX-License-Identifier: AGPL-3.0-or-later
*/
#ifndef _LIBHW_GENERIC_IO_H_
#define _LIBHW_GENERIC_IO_H_
#include <stddef.h> /* for size_t */
#include <stdint.h> /* for uintptr_t, uint{n}_t, UINT{n}_MAX */
#include <libmisc/error.h>
#include <libmisc/obj.h>
/* structs ********************************************************************/
/* uoff_t ==========================================================*/
typedef uint64_t uoff_t;
#define UOFF_MAX UINT64_MAX
DECLARE_ERROR_OR(uoff_t);
DECLARE_ERROR_AND(uoff_t);
/* iovec ===========================================================*/
#if __unix__
#include <sys/uio.h>
#else
struct iovec {
void *iov_base;
size_t iov_len;
};
#endif
typedef struct iovec iovec;
DECLARE_ERROR_OR(iovec);
DECLARE_ERROR_AND(iovec);
/* duplex_iovec ====================================================*/
#define IOVEC_DISCARD ((void*)(~((uintptr_t)0)))
struct duplex_iovec {
/**
* NULL is a valid pointer value in iov_read_to and
* iov_write_from. To skip a read or write, use the special
* value IOVEC_DISCARD.
*/
void *iov_read_to;
void *iov_write_from;
size_t iov_len;
};
typedef struct duplex_iovec duplex_iovec;
DECLARE_ERROR_OR(duplex_iovec);
DECLARE_ERROR_AND(duplex_iovec);
/* iovec utilities ************************************************************/
/* If byte_max_cnt == 0, then there is no maximum. */
/* slice iovec lists */
int io_slice_cnt ( const struct iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
void io_slice (struct iovec *dst, const struct iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
int io_duplex_slice_cnt( const struct duplex_iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
void io_duplex_slice (struct duplex_iovec *dst, const struct duplex_iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
/* convert iovec lists */
void io_rd_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int iovcnt);
void io_wr_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int iovcnt);
/* slice and convert in one go */
void io_slice_rd_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
void io_slice_wr_to_duplex(struct duplex_iovec *dst, const struct iovec *src, int src_cnt, size_t byte_start, size_t byte_max_cnt);
/* basic interfaces ***********************************************************/
/*
* Conventions:
*
* - Naming:
* + The "p"[osition] prefix means an explicit `uoff_t offset`,
* instead of using an internal cursor.
* + The "v"[ec] suffix means a sequence of iovecs, instead of a
* simple buf+len.
*
* - Errors:
* + Short *reads* are *not* errors (and so return size_t *or*
* error).
* + Short *writes* *are* errors (and so return size_t *and*
* (possibly-null) error).
*/
/* read ============================================================*/
/**
* Return bytes-read on success. A short read is *not* an error
* (unlike `write` methods).
*
* It is invalid to call readv when the sum length of iovecs is 0.
*/
#define io_reader_LO_IFACE \
LO_FUNC(size_t_or_error, readv, const struct iovec *iov, int iovcnt)
LO_INTERFACE(io_reader);
#define io_readv(r, iov, iovcnt) LO_CALL(r, readv, iov, iovcnt)
#define io_read(r, buf, count) LO_CALL(r, readv, &((struct iovec){.iov_base = buf, .iov_len = count}), 1)
/**
* Returns bytes-read on success. A short read is *not* an error
* (unlike `write` methods).
*
* It is invalid to call preadv when the sum length of iovecs is 0.
*/
#define io_preader_LO_IFACE \
LO_FUNC(size_t_or_error, preadv, const struct iovec *iov, int iovcnt, uoff_t offset)
LO_INTERFACE(io_preader);
#define io_preadv(r, iov, iovcnt, off) LO_CALL(r, preadv, iov, iovcnt, off)
#define io_pread(r, buf, count, off) LO_CALL(r, preadv, &((struct iovec){.iov_base = buf, .iov_len = count}), 1, off)
/* write ===========================================================*/
/**
* Return bytes-written. A short write *is* an error (unlike `read`
* methods).
*
* Writes are *not* guaranteed to be atomic, so if you have concurrent
* writers then you should arrange for a mutex to protect the writer.
*
* It is invalid to call writev when the sum length of iovecs is 0.
*/
#define io_writer_LO_IFACE \
LO_FUNC(size_t_and_error, writev, const struct iovec *iov, int iovcnt)
LO_INTERFACE(io_writer);
#define io_writev(w, iov, iovcnt) LO_CALL(w, writev, iov, iovcnt)
#define io_write(w, buf, count) LO_CALL(w, writev, &((struct iovec){.iov_base = buf, .iov_len = count}), 1)
/**
* Returns bytes-written. A short write *is* an error (unlike `read`
* methods).
*
* Writes are *not* guaranteed to be atomic, so if you have concurrent
* writers then you should arrange for a mutex to protect the writer.
*
* It is invalid to call writev when the sum length of iovecs is 0.
*/
#define io_pwriter_LO_IFACE \
LO_FUNC(size_t_and_error, pwritev, const struct iovec *iov, int iovcnt, uoff_t offset)
LO_INTERFACE(io_pwriter);
#define io_pwritev(r, iov, iovcnt, off) LO_CALL(r, pwritev, iov, iovcnt, off)
#define io_pwrite(r, buf, count, off) LO_CALL(r, pwritev, &((struct iovec){.iov_base = buf, .iov_len = count}), 1, off)
/* readwrite =======================================================*/
/**
* A short read/write *is* an error (like `write` methods and unlike
* `read` methods).
*
* Reads/writes are *not* guaranteed to be atomic, so if you have
* concurrent readers/writers then you should arrange for a mutex to
* protect the duplex_readwriter.
*
* It is invalid to call readwritev when the sum length of iovecs is 0.
*/
#define io_duplex_readwriter_LO_IFACE \
LO_FUNC(size_t_and_error, readwritev, const struct duplex_iovec *iov, int iovcnt)
LO_INTERFACE(io_duplex_readwriter);
#define io_readwritev(rw, iov, iovcnt) \
LO_CALL(rw, readwritev, iov, iovcnt)
/* read then write =================================================*/
/**
* LO_CALL(src, pread_to, dst, src_offset, count) is functionally:
*
* size_t_and_error copy(lo_interface io_writer dst, lo_interface io_preader src, uoff_t src_offset, size_t count) {
* buf = malloc(count);
* size_t_or_error read_r = io_pread(src, buf, count, src_offset);
* if (read_r.is_err)
* return ERROR_AND(size_t, 0, read_r.err);
* size_t_and_error write_r = io_write(dst, buf, read_r.size_t);
* free(buf);
* return write_r;
* }
*
* except that it does not need to allocate a buffer. That is: It
* allows the reader to dump its data directly to the writer. This
* allows us to save a copy when the reader already has an in-memory
* buffer containing the data.
*
* The above code defines when a short read/write is an error or not.
*
* It must call writev() exactly 0-or-1 times, and if it does call it,
* then it must be called with exactly 1 iovec.
*/
#define io_preader_to_LO_IFACE \
LO_FUNC(size_t_and_error, pread_to, lo_interface io_writer dst, uoff_t src_offset, size_t count)
LO_INTERFACE(io_preader_to);
/* close ===========================================================*/
#define io_closer_LO_IFACE \
LO_FUNC(error, close)
LO_INTERFACE(io_closer);
#define io_close(c) LO_CALL(c, close)
#define io_bidi_closer_LO_IFACE \
LO_NEST(io_closer) \
LO_FUNC(error, close_read) \
LO_FUNC(error, close_write)
LO_INTERFACE(io_bidi_closer);
#define io_close_read(c) LO_CALL(c, close_read)
#define io_close_write(c) LO_CALL(c, close_write)
/* aggregate interfaces *******************************************************/
#define io_readwriter_LO_IFACE \
LO_NEST(io_reader) \
LO_NEST(io_writer)
LO_INTERFACE(io_readwriter);
#endif /* _LIBHW_GENERIC_IO_H_ */
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