/*
- * Copyright 2013 Facebook, Inc.
+ * Copyright 2017 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* limitations under the License.
*/
-#ifndef FOLLY_FILEUTIL_H_
-#define FOLLY_FILEUTIL_H_
+#pragma once
-#include <sys/uio.h>
-#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <cassert>
+#include <limits>
+
+#include <folly/Portability.h>
+#include <folly/Range.h>
+#include <folly/ScopeGuard.h>
+#include <folly/portability/Fcntl.h>
+#include <folly/portability/SysUio.h>
+#include <folly/portability/Unistd.h>
namespace folly {
* until all data is written. Note that *Full wrappers weaken the thread
* semantics of underlying system calls.
*/
+int openNoInt(const char* name, int flags, mode_t mode = 0666);
int closeNoInt(int fd);
+int dupNoInt(int fd);
+int dup2NoInt(int oldfd, int newfd);
+int fsyncNoInt(int fd);
+int fdatasyncNoInt(int fd);
+int ftruncateNoInt(int fd, off_t len);
+int truncateNoInt(const char* path, off_t len);
+int flockNoInt(int fd, int operation);
+int shutdownNoInt(int fd, int how);
ssize_t readNoInt(int fd, void* buf, size_t n);
ssize_t preadNoInt(int fd, void* buf, size_t n, off_t offset);
* Note that writevFull and pwritevFull require iov to be non-const, unlike
* writev and pwritev. The contents of iov after these functions return
* is unspecified.
+ *
+ * These functions return -1 on error, or the total number of bytes written
+ * (which is always the same as the number of requested bytes) on success.
*/
ssize_t writeFull(int fd, const void* buf, size_t n);
ssize_t pwriteFull(int fd, const void* buf, size_t n, off_t offset);
ssize_t writevFull(int fd, iovec* iov, int count);
ssize_t pwritevFull(int fd, iovec* iov, int count, off_t offset);
-} // namespaces
+/**
+ * Read entire file (if num_bytes is defaulted) or no more than
+ * num_bytes (otherwise) into container *out. The container is assumed
+ * to be contiguous, with element size equal to 1, and offer size(),
+ * reserve(), and random access (e.g. std::vector<char>, std::string,
+ * fbstring).
+ *
+ * Returns: true on success or false on failure. In the latter case
+ * errno will be set appropriately by the failing system primitive.
+ */
+template <class Container>
+bool readFile(
+ int fd,
+ Container& out,
+ size_t num_bytes = std::numeric_limits<size_t>::max()) {
+ static_assert(sizeof(out[0]) == 1,
+ "readFile: only containers with byte-sized elements accepted");
+
+ size_t soFar = 0; // amount of bytes successfully read
+ SCOPE_EXIT {
+ DCHECK(out.size() >= soFar); // resize better doesn't throw
+ out.resize(soFar);
+ };
+
+ // Obtain file size:
+ struct stat buf;
+ if (fstat(fd, &buf) == -1) {
+ return false;
+ }
+ // Some files (notably under /proc and /sys on Linux) lie about
+ // their size, so treat the size advertised by fstat under advise
+ // but don't rely on it. In particular, if the size is zero, we
+ // should attempt to read stuff. If not zero, we'll attempt to read
+ // one extra byte.
+ constexpr size_t initialAlloc = 1024 * 4;
+ out.resize(
+ std::min(
+ buf.st_size > 0 ? (size_t(buf.st_size) + 1) : initialAlloc, num_bytes));
+
+ while (soFar < out.size()) {
+ const auto actual = readFull(fd, &out[soFar], out.size() - soFar);
+ if (actual == -1) {
+ return false;
+ }
+ soFar += actual;
+ if (soFar < out.size()) {
+ // File exhausted
+ break;
+ }
+ // Ew, allocate more memory. Use exponential growth to avoid
+ // quadratic behavior. Cap size to num_bytes.
+ out.resize(std::min(out.size() * 3 / 2, num_bytes));
+ }
+
+ return true;
+}
+
+/**
+ * Same as above, but takes in a file name instead of fd
+ */
+template <class Container>
+bool readFile(
+ const char* file_name,
+ Container& out,
+ size_t num_bytes = std::numeric_limits<size_t>::max()) {
+ DCHECK(file_name);
+
+ const auto fd = openNoInt(file_name, O_RDONLY);
+ if (fd == -1) {
+ return false;
+ }
+
+ SCOPE_EXIT {
+ // Ignore errors when closing the file
+ closeNoInt(fd);
+ };
-#endif /* FOLLY_FILEUTIL_H_ */
+ return readFile(fd, out, num_bytes);
+}
+
+/**
+ * Writes container to file. The container is assumed to be
+ * contiguous, with element size equal to 1, and offering STL-like
+ * methods empty(), size(), and indexed access
+ * (e.g. std::vector<char>, std::string, fbstring, StringPiece).
+ *
+ * "flags" dictates the open flags to use. Default is to create file
+ * if it doesn't exist and truncate it.
+ *
+ * Returns: true on success or false on failure. In the latter case
+ * errno will be set appropriately by the failing system primitive.
+ *
+ * Note that this function may leave the file in a partially written state on
+ * failure. Use writeFileAtomic() if you want to ensure that the existing file
+ * state will be unchanged on error.
+ */
+template <class Container>
+bool writeFile(const Container& data,
+ const char* filename,
+ int flags = O_WRONLY | O_CREAT | O_TRUNC,
+ mode_t mode = 0666) {
+ static_assert(sizeof(data[0]) == 1,
+ "writeFile works with element size equal to 1");
+ int fd = open(filename, flags, mode);
+ if (fd == -1) {
+ return false;
+ }
+ bool ok = data.empty() ||
+ writeFull(fd, &data[0], data.size()) == static_cast<ssize_t>(data.size());
+ return closeNoInt(fd) == 0 && ok;
+}
+
+/**
+ * Write file contents "atomically".
+ *
+ * This writes the data to a temporary file in the destination directory, and
+ * then renames it to the specified path. This guarantees that the specified
+ * file will be replaced the the specified contents on success, or will not be
+ * modified on failure.
+ *
+ * Note that on platforms that do not provide atomic filesystem rename
+ * functionality (e.g., Windows) this behavior may not be truly atomic.
+ */
+void writeFileAtomic(
+ StringPiece filename,
+ iovec* iov,
+ int count,
+ mode_t permissions = 0644);
+void writeFileAtomic(
+ StringPiece filename,
+ ByteRange data,
+ mode_t permissions = 0644);
+void writeFileAtomic(
+ StringPiece filename,
+ StringPiece data,
+ mode_t permissions = 0644);
+
+/**
+ * A version of writeFileAtomic() that returns an errno value instead of
+ * throwing on error.
+ *
+ * Returns 0 on success or an errno value on error.
+ */
+int writeFileAtomicNoThrow(
+ StringPiece filename,
+ iovec* iov,
+ int count,
+ mode_t permissions = 0644);
+} // namespace folly
projects / folly.git / blobdiff