diff options
Diffstat (limited to 'src/port/pread.c')
| -rw-r--r-- | src/port/pread.c | 43 |
1 files changed, 41 insertions, 2 deletions
diff --git a/src/port/pread.c b/src/port/pread.c index 486f07a7dff..a5ae2759fa0 100644 --- a/src/port/pread.c +++ b/src/port/pread.c @@ -1,7 +1,7 @@ /*------------------------------------------------------------------------- * * pread.c - * Implementation of pread(2) for platforms that lack one. + * Implementation of pread[v](2) for platforms that lack one. * * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group * @@ -9,7 +9,8 @@ * src/port/pread.c * * Note that this implementation changes the current file position, unlike - * the POSIX function, so we use the name pg_pread(). + * the POSIX function, so we use the name pg_pread(). Likewise for the + * iovec version. * *------------------------------------------------------------------------- */ @@ -23,6 +24,9 @@ #include <unistd.h> #endif +#include "port/pg_iovec.h" + +#ifndef HAVE_PREAD ssize_t pg_pread(int fd, void *buf, size_t size, off_t offset) { @@ -56,3 +60,38 @@ pg_pread(int fd, void *buf, size_t size, off_t offset) return read(fd, buf, size); #endif } +#endif + +#ifndef HAVE_PREADV +ssize_t +pg_preadv(int fd, const struct iovec *iov, int iovcnt, off_t offset) +{ +#ifdef HAVE_READV + if (iovcnt == 1) + return pg_pread(fd, iov[0].iov_base, iov[0].iov_len, offset); + if (lseek(fd, offset, SEEK_SET) < 0) + return -1; + return readv(fd, iov, iovcnt); +#else + ssize_t sum = 0; + ssize_t part; + + for (int i = 0; i < iovcnt; ++i) + { + part = pg_pread(fd, iov[i].iov_base, iov[i].iov_len, offset); + if (part < 0) + { + if (i == 0) + return -1; + else + return sum; + } + sum += part; + offset += part; + if (part < iov[i].iov_len) + return sum; + } + return sum; +#endif +} +#endif |