diff --git a/include/fcntl.h b/include/fcntl.h index 00e7a496ea..f49af928af 100644 --- a/include/fcntl.h +++ b/include/fcntl.h @@ -109,6 +109,13 @@ #define F_WRLCK 1 /* Take out a write lease */ #define F_UNLCK 2 /* Remove a lease */ +/* Operations for bsd flock(), also used by the kernel implementation */ + +#define LOCK_SH 1 /* Shared lock */ +#define LOCK_EX 2 /* Exclusive lock */ +#define LOCK_NB 4 /* Or'd with one of the above to prevent blocking */ +#define LOCK_UN 8 /* Remove lock */ + /* close-on-exec flag for F_GETFD and F_SETFD */ #define FD_CLOEXEC 1 diff --git a/include/sys/file.h b/include/sys/file.h index 53767c3829..7f48e93f00 100644 --- a/include/sys/file.h +++ b/include/sys/file.h @@ -28,4 +28,23 @@ #include #include +/**************************************************************************** + * Public Function Prototypes + ****************************************************************************/ + +#ifdef __cplusplus +#define EXTERN extern "C" +extern "C" +{ +#else +#define EXTERN extern +#endif + +int flock(int fd, int cmd); + +#undef EXTERN +#ifdef __cplusplus +} +#endif + #endif /* __INCLUDE_SYS_FILE_H */ diff --git a/libs/libc/unistd/CMakeLists.txt b/libs/libc/unistd/CMakeLists.txt index 8783b8225e..e2b3d28a74 100644 --- a/libs/libc/unistd/CMakeLists.txt +++ b/libs/libc/unistd/CMakeLists.txt @@ -62,6 +62,7 @@ set(SRCS lib_linkat.c lib_readlinkat.c lib_symlinkat.c + lib_flock.c lib_unlinkat.c) if(NOT CONFIG_SCHED_USER_IDENTITY) diff --git a/libs/libc/unistd/Make.defs b/libs/libc/unistd/Make.defs index 6605e2fdbd..f15c29b297 100644 --- a/libs/libc/unistd/Make.defs +++ b/libs/libc/unistd/Make.defs @@ -30,7 +30,7 @@ CSRCS += lib_setrlimit.c lib_getrlimit.c lib_setpriority.c lib_getpriority.c CSRCS += lib_futimes.c lib_lutimes.c lib_gethostname.c lib_sethostname.c CSRCS += lib_fchownat.c lib_linkat.c lib_readlinkat.c lib_symlinkat.c CSRCS += lib_unlinkat.c lib_usleep.c lib_getpgrp.c lib_getpgid.c -CSRCS += lib_lockf.c +CSRCS += lib_lockf.c lib_flock.c ifneq ($(CONFIG_SCHED_USER_IDENTITY),y) CSRCS += lib_setuid.c lib_setgid.c lib_getuid.c lib_getgid.c diff --git a/libs/libc/unistd/lib_flock.c b/libs/libc/unistd/lib_flock.c new file mode 100644 index 0000000000..8e2b33ef66 --- /dev/null +++ b/libs/libc/unistd/lib_flock.c @@ -0,0 +1,95 @@ +/**************************************************************************** + * libs/libc/unistd/lib_flock.c + * + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. The + * ASF licenses this file to you under the Apache License, Version 2.0 (the + * "License"); you may not use this file except in compliance with the + * License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT + * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the + * License for the specific language governing permissions and limitations + * under the License. + * + ****************************************************************************/ + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include +#include +#include + +/**************************************************************************** + * Public Functions + ****************************************************************************/ + +/**************************************************************************** + * Name: flock + * + * Description: + * flock() is a function that allows a process to apply or remove an + * advisory lock on an open file. The lock can be either a shared (read) + * lock or an exclusive (write) lock. This lock is advisory, meaning that + * it is not enforced by the system and it is up to cooperating processes + * to honor the lock. + * + * Input Parameters: + * fd - File descriptor of the open file. + * cmd - Specifies the type of lock operation to be performed. + * It can be one of the following: + * LOCK_SH: Request a shared (read) lock. If the lock is not available. + * LOCK_EX: Request an exclusive (write) lock. If the lock is not + * available. + * LOCK_UN: Unlock an existing lock. + * LOCK_NB: Do not block when locking. + * + * Returned Value: + * The returned value of flock() depends on the success or failure of the + * operation. On success, the return value is 0. On failure, the return + * value is -1, and the errno variable is set to indicate the specific + * error. + * + ****************************************************************************/ + +int flock(int fd, int cmd) +{ + struct flock lock; + + lock.l_whence = SEEK_SET; + lock.l_start = 0; + lock.l_len = 0; + + if ((cmd & LOCK_SH) != 0) + { + lock.l_type = F_RDLCK; + } + else if ((cmd & LOCK_EX) != 0) + { + lock.l_type = F_WRLCK; + } + else if ((cmd & LOCK_UN) != 0) + { + lock.l_type = F_UNLCK; + } + else + { + set_errno(EINVAL); + return ERROR; + } + + if ((cmd & LOCK_NB) != 0) + { + return fcntl(fd, F_SETLK, &lock); + } + else + { + return fcntl(fd, F_SETLKW, &lock); + } +}