path: root/util.c

/*
 * Copyright (C) 2006-2009 Andre Noll <maan@tuebingen.mpg.de>
 *
 * Licensed under the GPL v2. For licencing details see COPYING.
 */

/** \file util.c Helper functions needed by both libosl and oslfsck. */

#include <sys/types.h>
#include <dirent.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <sys/select.h>

#include "log.h"
#include "osl.h"
#include "util.h"

/**
 * Wrapper for the write system call.
 *
 * \param fd The file descriptor to write to.
 * \param buf The buffer to write.
 * \param size The length of \a buf in bytes.
 *
 * This function writes out the given buffer and retries if an interrupt
 * occurred during the write.
 *
 * \return On success, the number of bytes written is returned, otherwise, a
 * negative error code is returned.
 *
 * \sa write(2).
 */
static ssize_t __write(int fd, const void *buf, size_t size)
{
	ssize_t ret;

	for (;;) {
		ret = write(fd, buf, size);
		if ((ret < 0) && (errno == EAGAIN || errno == EINTR))
			continue;
		return ret >= 0? ret : -E_OSL_WRITE;
	}
}

/**
 * Write a buffer to a file descriptor, re-write on short writes.
 *
 * \param fd The file descriptor.
 * \param buf The buffer to be sent.
 * \param len The length of \a buf.
 *
 * \return Standard. In any case, the number of bytes that have been written is
 * stored in \a len.
 */
int write_all(int fd, const char *buf, size_t *len)
{
	size_t total = *len;

	assert(total);
	*len = 0;
	while (*len < total) {
		int ret = __write(fd, buf + *len, total - *len);
		if (ret < 0) {
			ERROR_LOG("write error: %s\n", strerror(errno));
			return ret;
		}
		*len += ret;
	}
	return 1;
}

/**
 * Wrapper for the open(2) system call.
 *
 * \param path The filename.
 * \param flags The usual open(2) flags.
 * \param mode Specifies the permissions to use.
 *
 * The mode parameter must be specified when O_CREAT is in the flags, and is
 * ignored otherwise.
 *
 * \return The file descriptor on success, negative on errors.
 *
 * \sa open(2).
 */
int osl_open(const char *path, int flags, mode_t mode)
{
	int ret = open(path, flags, mode);

	if (ret >= 0)
		return ret;
	return errno == ENOENT? -E_OSL_NOENT : -E_OSL_OPEN;
}

/**
 * Open a file, write the given buffer and close the file.
 *
 * \param filename Full path to the file to open.
 * \param buf The buffer to write to the file.
 * \param size The size of \a buf.
 *
 * \return Standard.
 */
int write_file(const char *filename, const void *buf, size_t size)
{
	int ret, fd;

	ret = osl_open(filename, O_WRONLY | O_CREAT | O_EXCL, 0644);
	if (ret < 0)
		return ret;
	fd = ret;
	if (size != 0) {
		ret = write_all(fd, buf, &size);
		if (ret < 0)
			goto out;
	}
	ret = 1;
out:
	close(fd);
	return ret;
}

/**
 * Open a file and map it into memory.
 *
 * \param path Name of the regular file to map.
 * \param open_mode Either \p O_RDONLY or \p O_RDWR.
 * \param map On success, the mapping is returned here.
 * \param size size of the mapping.
 * \param fd_ptr The file descriptor of the mapping.
 *
 * If \a fd_ptr is \p NULL, the file descriptor resulting from the underlying
 * open call is closed after mmap().  Otherwise the file is kept open and the
 * file descriptor is returned in \a fd_ptr.
 *
 * \return Standard.
 *
 * \sa osl_open(), mmap(2).
 */
int mmap_full_file(const char *path, int open_mode, void **map,
		size_t *size, int *fd_ptr)
{
	int fd, ret, mmap_prot, mmap_flags;
	struct stat file_status;

	if (open_mode == O_RDONLY) {
		mmap_prot = PROT_READ;
		mmap_flags = MAP_PRIVATE;
	} else {
		mmap_prot = PROT_READ | PROT_WRITE;
		mmap_flags = MAP_SHARED;
	}
	ret = osl_open(path, open_mode, 0);
	if (ret < 0)
		return ret;
	fd = ret;
	if (fstat(fd, &file_status) < 0) {
		ret = errno == ENOENT? -E_OSL_NOENT : -E_OSL_STAT;
		goto out;
	}
	*size = file_status.st_size;
	ret = -E_OSL_EMPTY;
	DEBUG_LOG("%s: size %zu\n", path, *size);
	if (!*size)
		goto out;
	*map = mmap(NULL, *size, mmap_prot, mmap_flags, fd, 0);
	if (*map == MAP_FAILED) {
		*map = NULL;
		ret = -E_OSL_MMAP;
		goto out;
	}
	ret = 1;
out:
	if (ret < 0 || !fd_ptr)
		close(fd);
	else
		*fd_ptr = fd;
	return ret;
}

/**
 * A wrapper for munmap(2).
 *
 * \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.
 *
 * \sa munmap(2), mmap_full_file().
 */
int osl_munmap(void *start, size_t length)
{
	int err;
	if (munmap(start, length) >= 0)
		return 1;
	err = errno;
	ERROR_LOG("munmap (%p/%zu) failed: %s\n", start, length,
		strerror(err));
	return -E_OSL_MUNMAP;
}

/**
 * Allocate a sufficiently large string and print into it.
 *
 * \param fmt A usual format string.
 *
 * Produce output according to \p fmt. No artificial bound on the length of the
 * resulting string is imposed.
 *
 * \return This function either returns a pointer to a string that must be
 * freed by the caller or \p NULL if memory allocation failed.
 *
 * \sa printf(3).
 */
__must_check __printf_1_2 __malloc char *make_message(const char *fmt, ...)
{
	int n;
	size_t size = 100;
	char *p = malloc(size);

	if (!p)
		return NULL;
	while (1) {
		char *q;
		va_list ap;
		/* Try to print in the allocated space. */
		va_start(ap, fmt);
		n = vsnprintf(p, size, fmt, ap);
		va_end(ap);
		/* If that worked, return the string. */
		if (n > -1 && (unsigned)n < size)
			break;
		/* Else try again with more space. */
		if (n > -1) /* glibc 2.1 */
			size = n + 1; /* precisely what is needed */
		else /* glibc 2.0 */
			size *= 2; /* twice the old size */
		q = realloc(p, size);
		if (!q) {
			free(p);
			return NULL;
		}
		p = q;
	}
	return p;
}

/**
 * A wrapper for truncate(2)
 *
 * \param path Name of the regular file to truncate
 * \param size Number of bytes to \b shave \b off
 *
 * Truncate the regular file named by \a path by \a size bytes.
 *
 * \return Standard.
 *
 * \sa truncate(2)
 */
int truncate_file(const char *path, off_t size)
{
	int ret;
	struct stat statbuf;

	ret = osl_stat(path, &statbuf);
	if (ret < 0)
		return ret;
	ret = -E_OSL_BAD_SIZE;
	if (statbuf.st_size < size)
		return ret;
	if (truncate(path, statbuf.st_size - size) < 0)
		return -E_OSL_TRUNCATE;
	return 1;
}