diff options
| -rw-r--r-- | libhw_generic/include/libhw/generic/io.h | 69 |
1 files changed, 67 insertions, 2 deletions
diff --git a/libhw_generic/include/libhw/generic/io.h b/libhw_generic/include/libhw/generic/io.h index 19edbe6..c615932 100644 --- a/libhw_generic/include/libhw/generic/io.h +++ b/libhw_generic/include/libhw/generic/io.h @@ -7,14 +7,21 @@ #ifndef _LIBHW_GENERIC_IO_H_ #define _LIBHW_GENERIC_IO_H_ -#include <stddef.h> /* for size_t */ -#include <stdint.h> /* for uintptr_t */ +#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__ @@ -71,6 +78,8 @@ void io_slice_wr_to_duplex(struct duplex_iovec *dst, const struct iovec *src, in * 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. * @@ -95,6 +104,18 @@ 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 ===========================================================*/ /** @@ -112,6 +133,21 @@ 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 =======================================================*/ /** @@ -130,6 +166,35 @@ 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 \ |