X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=fd.c;h=bdba2765a0fe3c6be12a9b32679bd79c267c6eb3;hp=1c67f22bb284ab11ffda80bb90c0693661b0328c;hb=60ef885705932a682097ad2b9f2379282d814e79;hpb=03d45daad787b8f2ced3070e80c4550bf4b02931 diff --git a/fd.c b/fd.c index 1c67f22b..bdba2765 100644 --- a/fd.c +++ b/fd.c @@ -1,20 +1,23 @@ /* - * Copyright (C) 2006-2009 Andre Noll + * Copyright (C) 2006-2010 Andre Noll * * Licensed under the GPL v2. For licencing details see COPYING. */ /** \file fd.c Helper functions for file descriptor handling. */ +#include #include #include #include #include -#include +#include #include "para.h" #include "error.h" #include "string.h" +#include "fd.h" + /** * Write a buffer to a file descriptor, re-write on short writes. * @@ -79,6 +82,146 @@ int write_nonblock(int fd, const char *buf, size_t len, return written; } +/** + * Read from a non-blocking file descriptor into multiple buffers. + * + * \param fd The file descriptor to read from. + * \param iov Scatter/gather array used in readv(). + * \param iovcnt Number of elements in \a iov. + * \param rfds An optional fd set pointer. + * \param num_bytes Result pointer. Contains the number of bytes read from \a fd. + * + * If \a rfds is not \p NULL and the (non-blocking) file descriptor \a fd is + * not set in \a rfds, this function returns early without doing anything. + * Otherwise The function tries to read up to \a sz bytes from \a fd. As for + * write_nonblock(), EAGAIN is not considered an error condition. However, EOF + * is. + * + * \return Zero or a negative error code. If the underlying call to readv(2) + * returned zero (indicating an end of file condition) or failed for some + * reason other than \p EAGAIN, a negative return value is returned. + * + * In any case, \a num_bytes contains the number of bytes that have been + * successfully read from \a fd (zero if the first readv() call failed with + * EAGAIN). Note that even if the function returns negative, some data might + * have been read before the error occured. In this case \a num_bytes is + * positive. + * + * \sa \ref write_nonblock(), read(2), readv(2). + */ +int readv_nonblock(int fd, struct iovec *iov, int iovcnt, fd_set *rfds, + size_t *num_bytes) +{ + int ret, i, j; + + *num_bytes = 0; + /* + * Avoid a shortcoming of select(): Reads from a non-blocking fd might + * return EAGAIN even if FD_ISSET() returns true. However, FD_ISSET() + * returning false definitely means that no data can currently be read. + * This is the common case, so it is worth to avoid the overhead of the + * read() system call in this case. + */ + if (rfds && !FD_ISSET(fd, rfds)) + return 0; + + for (i = 0, j = 0; i < iovcnt;) { + + /* fix up the first iov */ + assert(j < iov[i].iov_len); + iov[i].iov_base += j; + iov[i].iov_len -= j; + ret = readv(fd, iov + i, iovcnt - i); + iov[i].iov_base -= j; + iov[i].iov_len += j; + + if (ret == 0) + return -E_EOF; + if (ret < 0) { + if (errno == EAGAIN) + return 0; + return -ERRNO_TO_PARA_ERROR(errno); + } + *num_bytes += ret; + while (ret > 0) { + if (ret < iov[i].iov_len - j) { + j += ret; + break; + } + ret -= iov[i].iov_len - j; + j = 0; + if (++i >= iovcnt) + break; + } + } + return 0; +} + +/** + * Read from a non-blocking file descriptor into a single buffer. + * + * \param fd The file descriptor to read from. + * \param buf The buffer to read data to. + * \param sz The size of \a buf. + * \param rfds \see \ref readv_nonblock(). + * \param num_bytes \see \ref readv_nonblock(). + * + * This is a simple wrapper for readv_nonblock() which uses an iovec with a single + * buffer. + * + * \return The return value of the underlying call to readv_nonblock(). + */ +int read_nonblock(int fd, void *buf, size_t sz, fd_set *rfds, size_t *num_bytes) +{ + struct iovec iov = {.iov_base = buf, .iov_len = sz}; + return readv_nonblock(fd, &iov, 1, rfds, num_bytes); +} + +/** + * Read a buffer and check its content for a pattern. + * + * \param fd The file descriptor to receive from. + * \param pattern The expected pattern. + * \param bufsize The size of the internal buffer. + * + * This function tries to read at most \a bufsize bytes from the non-blocking + * file descriptor \a fd. If at least \p strlen(\a pattern) bytes have been + * received, the beginning of the received buffer is compared with \a pattern, + * ignoring case. + * + * \return Positive if \a pattern was received, negative on errors, zero if no data + * was available to read. + * + * \sa \ref read_nonblock(), \sa strncasecmp(3). + */ +int read_pattern(int fd, const char *pattern, size_t bufsize, fd_set *rfds) +{ + size_t n, len; + char *buf = para_malloc(bufsize + 1); + int ret = read_nonblock(fd, buf, bufsize, rfds, &n); + + buf[n] = '\0'; + if (ret < 0) + goto out; + ret = 0; + if (n == 0) + goto out; + ret = -E_READ_PATTERN; + len = strlen(pattern); + if (n < len) + goto out; + if (strncasecmp(buf, pattern, len) != 0) + goto out; + ret = 1; +out: + if (ret < 0) { + PARA_NOTICE_LOG("%s\n", para_strerror(-ret)); + PARA_NOTICE_LOG("recvd %zu bytes: %s\n", n, buf); + } + free(buf); + return ret; +} + /** * Check whether a file exists. * @@ -114,11 +257,10 @@ int file_exists(const char *fn) int para_select(int n, fd_set *readfds, fd_set *writefds, struct timeval *timeout_tv) { - int ret, err; - do { + int ret; + do ret = select(n, readfds, writefds, NULL, timeout_tv); - err = errno; - } while (ret < 0 && err == EINTR); + while (ret < 0 && errno == EINTR); if (ret < 0) return -ERRNO_TO_PARA_ERROR(errno); return ret; @@ -420,7 +562,7 @@ out: * \param start The start address of the memory mapping. * \param length The size of the mapping. * - * \return Positive on success, \p -E_MUNMAP on errors. + * \return Standard. * * \sa munmap(2), mmap_full_file(). */ @@ -446,18 +588,14 @@ int para_munmap(void *start, size_t length) int write_ok(int fd) { - struct timeval tv = {0, 0}; + struct timeval tv; fd_set wfds; - int ret; -again: + FD_ZERO(&wfds); FD_SET(fd, &wfds); tv.tv_sec = 0; tv.tv_usec = 0; - ret = select(fd + 1, NULL, &wfds, NULL, &tv); - if (ret < 0 && errno == EINTR) - goto again; - return ret; + return para_select(fd + 1, NULL, &wfds, &tv); } /**