Mbed OS Reference | mbed_retarget.h Source File

 /*
  * mbed Microcontroller Library
  * Copyright (c) 2006-2016 ARM Limited
  * SPDX-License-Identifier: Apache-2.0
  *
  * Licensed 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.
  *
  */
 
 #ifndef RETARGET_H
 #define RETARGET_H
 
 #if __cplusplus
 #include <cstdio>
 #else
 #include <stdio.h>
 #endif //__cplusplus
 #include <stdint.h>
 #include <stddef.h>
 
 /* Include logic for errno so we can get errno defined but not bring in error_t,
  * including errno here prevents an include later, which would redefine our
  * error codes
  */
 #ifndef __error_t_defined
 #define __error_t_defined 1
 #include <errno.h>
 #undef __error_t_defined
 #else
 #include <errno.h>
 #endif
 
 /* We can get the following standard types from sys/types for gcc, but we
  * need to define the types ourselves for the other compilers that normally
  * target embedded systems */
 typedef signed   int  ssize_t;  ///< Signed size type, usually encodes negative errors
 typedef signed   long off_t;    ///< Offset in a data stream
 typedef unsigned int  nfds_t;   ///< Number of file descriptors
 typedef unsigned long long fsblkcnt_t;  ///< Count of file system blocks
 #if defined(__ARMCC_VERSION) || !defined(__GNUC__)
 typedef unsigned int  mode_t;   ///< Mode for opening files
 typedef unsigned int  dev_t;    ///< Device ID type
 typedef unsigned long ino_t;    ///< File serial number
 typedef unsigned int  nlink_t;  ///< Number of links to a file
 typedef unsigned int  uid_t;    ///< User ID
 typedef unsigned int  gid_t;    ///< Group ID
 #endif
 
 /* Flags for open() and fcntl(GETFL/SETFL)
  * At present, fcntl only supports reading and writing O_NONBLOCK
  */
 #define O_RDONLY 0        ///< Open for reading
 #define O_WRONLY 1        ///< Open for writing
 #define O_RDWR   2        ///< Open for reading and writing
 #define O_NONBLOCK 0x0004 ///< Non-blocking mode
 #define O_APPEND   0x0008 ///< Set file offset to end of file prior to each write
 #define O_CREAT    0x0200 ///< Create file if it does not exist
 #define O_TRUNC    0x0400 ///< Truncate file to zero length
 #define O_EXCL     0x0800 ///< Fail if file exists
 #define O_BINARY   0x8000 ///< Open file in binary mode
 
 #define O_ACCMODE   (O_RDONLY|O_WRONLY|O_RDWR)
 
 #define NAME_MAX 255    ///< Maximum size of a name in a file path
 
 #define STDIN_FILENO  0
 #define STDOUT_FILENO 1
 #define STDERR_FILENO 2
 
 #include <time.h>
 
 /** \addtogroup platform */
 /** @{*/
 /**
  * \defgroup platform_retarget Retarget functions
  * @{
  */
 
 /* DIR declarations must also be here */
 #if __cplusplus
 namespace mbed {
 
 class FileHandle;
 class DirHandle;
 
 /** Targets may implement this to change stdin, stdout, stderr.
  *
  * If the application hasn't provided mbed_override_console, this is called
  * to give the target a chance to specify a FileHandle for the console.
  *
  * If this is not provided or returns NULL, the console will be:
  *   - UARTSerial if configuration option "platform.stdio-buffered-serial" is
  *     true and the target has DEVICE_SERIAL;
  *   - Raw HAL serial via serial_getc and serial_putc if
  *     "platform.stdio-buffered-serial" is false and the target has DEVICE_SERIAL;
  *   - stdout/stderr will be a sink and stdin will input a stream of 0s if the
  *     target does not have DEVICE_SERIAL.
  *
  * @param fd file descriptor - STDIN_FILENO, STDOUT_FILENO or STDERR_FILENO
  * @return  pointer to FileHandle to override normal stream otherwise NULL
  */
 FileHandle *mbed_target_override_console(int fd);
 
 /** Applications may implement this to change stdin, stdout, stderr.
  *
  * This hook gives the application a chance to specify a custom FileHandle
  * for the console.
  *
  * If this is not provided or returns NULL, the console will be specified
  * by mbed_target_override_console, else will default to serial - see
  * mbed_target_override_console for more details.
  *
  * Example using UARTSerial:
  * @code
  * FileHandle *mbed::mbed_override_console(int) {
  *     static UARTSerial my_serial(D0, D1);
  *     return &my_serial;
  * }
  * @endcode
  *
  * Example using SingleWireOutput:
  * @code
  * FileHandle *mbed::mbed_override_console(int) {
  *     static SerialWireOutput swo;
  *     return &swo;
  * }
  * @endcode
  *
  * Example using arm semihosting:
  * @code
  * FileHandle *mbed::mbed_override_console(int fileno) {
  *    static LocalFileSystem fs("host");
  *    if (fileno == STDIN_FILENO) {
  *        static FileHandle *in_terminal;
  *        static int in_open_result = fs.open(&in_terminal, ":tt", O_RDONLY);
  *        return in_terminal;
  *    } else {
  *        static FileHandle *out_terminal;
  *        static int out_open_result = fs.open(&out_terminal, ":tt", O_WRONLY);
  *        return out_terminal;
  *    }
  * }
  * @endcode
  *
  * @param fd file descriptor - STDIN_FILENO, STDOUT_FILENO or STDERR_FILENO
  * @return  pointer to FileHandle to override normal stream otherwise NULL
  */
 FileHandle *mbed_override_console(int fd);
 
 /** Look up the Mbed file handle corresponding to a file descriptor
  *
  * This conversion function permits an application to find the underlying
  * FileHandle object corresponding to a POSIX file descriptor.
  *
  * This allows access to specialized behavior only available via the
  * FileHandle API.
  *
  * Example of saving power by disabling console input - for buffered serial,
  * this would release the RX interrupt handler, which would release the
  * deep sleep lock.
  * @code
  * mbed_file_handle(STDIN_FILENO)->enable_input(false);
  * @endcode
  *
  * @param fd file descriptor
  * @return   FileHandle pointer
  *           NULL if descriptor does not correspond to a FileHandle (only
  *           possible if it's not open with current implementation).
  */
 FileHandle *mbed_file_handle(int fd);
 }
 
 typedef mbed::DirHandle DIR;
 #else
 typedef struct Dir DIR;
 #endif
 
 /* The intent of this section is to unify the errno error values to match
  * the POSIX definitions for the GCC_ARM, ARMCC and IAR compilers. This is
  * necessary because the ARMCC/IAR errno.h, or sys/stat.h are missing some
  * symbol definitions used by the POSIX filesystem API to return errno codes.
  * Note also that ARMCC errno.h defines some symbol values differently from
  * the GCC_ARM/IAR/standard POSIX definitions. The definitions guard against
  * this and future changes by changing the symbol definition as shown below.
  */
 #undef  EPERM
 #define EPERM           1       /* Operation not permitted */
 #undef  ENOENT
 #define ENOENT          2       /* No such file or directory */
 #undef  ESRCH
 #define ESRCH           3       /* No such process */
 #undef  EINTR
 #define EINTR           4       /* Interrupted system call */
 #undef  EIO
 #define EIO             5       /* I/O error */
 #undef  ENXIO
 #define ENXIO           6       /* No such device or address */
 #undef  E2BIG
 #define E2BIG           7       /* Argument list too long */
 #undef  ENOEXEC
 #define ENOEXEC         8       /* Exec format error */
 #undef  EBADF
 #define EBADF           9       /* Bad file number */
 #undef  ECHILD
 #define ECHILD          10      /* No child processes */
 #undef  EAGAIN
 #define EAGAIN          11      /* Try again */
 #undef  ENOMEM
 #define ENOMEM          12      /* Out of memory */
 #undef  EACCES
 #define EACCES          13      /* Permission denied */
 #undef  EFAULT
 #define EFAULT          14      /* Bad address */
 #undef  ENOTBLK
 #define ENOTBLK         15      /* Block device required */
 #undef  EBUSY
 #define EBUSY           16      /* Device or resource busy */
 #undef  EEXIST
 #define EEXIST          17      /* File exists */
 #undef  EXDEV
 #define EXDEV           18      /* Cross-device link */
 #undef  ENODEV
 #define ENODEV          19      /* No such device */
 #undef  ENOTDIR
 #define ENOTDIR         20      /* Not a directory */
 #undef  EISDIR
 #define EISDIR          21      /* Is a directory */
 #undef  EINVAL
 #define EINVAL          22      /* Invalid argument */
 #undef  ENFILE
 #define ENFILE          23      /* File table overflow */
 #undef  EMFILE
 #define EMFILE          24      /* Too many open files */
 #undef  ENOTTY
 #define ENOTTY          25      /* Not a typewriter */
 #undef  ETXTBSY
 #define ETXTBSY         26      /* Text file busy */
 #undef  EFBIG
 #define EFBIG           27      /* File too large */
 #undef  ENOSPC
 #define ENOSPC          28      /* No space left on device */
 #undef  ESPIPE
 #define ESPIPE          29      /* Illegal seek */
 #undef  EROFS
 #define EROFS           30      /* Read-only file system */
 #undef  EMLINK
 #define EMLINK          31      /* Too many links */
 #undef  EPIPE
 #define EPIPE           32      /* Broken pipe */
 #undef  EDOM
 #define EDOM            33      /* Math argument out of domain of func */
 #undef  ERANGE
 #define ERANGE          34      /* Math result not representable */
 #undef  EDEADLK
 #define EDEADLK         35      /* Resource deadlock would occur */
 #undef  ENAMETOOLONG
 #define ENAMETOOLONG    36      /* File name too long */
 #undef  ENOLCK
 #define ENOLCK          37      /* No record locks available */
 #undef  ENOSYS
 #define ENOSYS          38      /* Function not implemented */
 #undef  ENOTEMPTY
 #define ENOTEMPTY       39      /* Directory not empty */
 #undef  ELOOP
 #define ELOOP           40      /* Too many symbolic links encountered */
 #undef  EWOULDBLOCK
 #define EWOULDBLOCK     EAGAIN  /* Operation would block */
 #undef  ENOMSG
 #define ENOMSG          42      /* No message of desired type */
 #undef  EIDRM
 #define EIDRM           43      /* Identifier removed */
 #undef  ECHRNG
 #define ECHRNG          44      /* Channel number out of range */
 #undef  EL2NSYNC
 #define EL2NSYNC        45      /* Level 2 not synchronized */
 #undef  EL3HLT
 #define EL3HLT          46      /* Level 3 halted */
 #undef  EL3RST
 #define EL3RST          47      /* Level 3 reset */
 #undef  ELNRNG
 #define ELNRNG          48      /* Link number out of range */
 #undef  EUNATCH
 #define EUNATCH         49      /* Protocol driver not attached */
 #undef  ENOCSI
 #define ENOCSI          50      /* No CSI structure available */
 #undef  EL2HLT
 #define EL2HLT          51      /* Level 2 halted */
 #undef  EBADE
 #define EBADE           52      /* Invalid exchange */
 #undef  EBADR
 #define EBADR           53      /* Invalid request descriptor */
 #undef  EXFULL
 #define EXFULL          54      /* Exchange full */
 #undef  ENOANO
 #define ENOANO          55      /* No anode */
 #undef  EBADRQC
 #define EBADRQC         56      /* Invalid request code */
 #undef  EBADSLT
 #define EBADSLT         57      /* Invalid slot */
 #undef  EDEADLOCK
 #define EDEADLOCK       EDEADLK /* Resource deadlock would occur */
 #undef  EBFONT
 #define EBFONT          59      /* Bad font file format */
 #undef  ENOSTR
 #define ENOSTR          60      /* Device not a stream */
 #undef  ENODATA
 #define ENODATA         61      /* No data available */
 #undef  ETIME
 #define ETIME           62      /* Timer expired */
 #undef  ENOSR
 #define ENOSR           63      /* Out of streams resources */
 #undef  ENONET
 #define ENONET          64      /* Machine is not on the network */
 #undef  ENOPKG
 #define ENOPKG          65      /* Package not installed */
 #undef  EREMOTE
 #define EREMOTE         66      /* Object is remote */
 #undef  ENOLINK
 #define ENOLINK         67      /* Link has been severed */
 #undef  EADV
 #define EADV            68      /* Advertise error */
 #undef  ESRMNT
 #define ESRMNT          69      /* Srmount error */
 #undef  ECOMM
 #define ECOMM           70      /* Communication error on send */
 #undef  EPROTO
 #define EPROTO          71      /* Protocol error */
 #undef  EMULTIHOP
 #define EMULTIHOP       72      /* Multihop attempted */
 #undef  EDOTDOT
 #define EDOTDOT         73      /* RFS specific error */
 #undef  EBADMSG
 #define EBADMSG         74      /* Not a data message */
 #undef  EOVERFLOW
 #define EOVERFLOW       75      /* Value too large for defined data type */
 #undef  ENOTUNIQ
 #define ENOTUNIQ        76      /* Name not unique on network */
 #undef  EBADFD
 #define EBADFD          77      /* File descriptor in bad state */
 #undef  EREMCHG
 #define EREMCHG         78      /* Remote address changed */
 #undef  ELIBACC
 #define ELIBACC         79      /* Can not access a needed shared library */
 #undef  ELIBBAD
 #define ELIBBAD         80      /* Accessing a corrupted shared library */
 #undef  ELIBSCN
 #define ELIBSCN         81      /* .lib section in a.out corrupted */
 #undef  ELIBMAX
 #define ELIBMAX         82      /* Attempting to link in too many shared libraries */
 #undef  ELIBEXEC
 #define ELIBEXEC        83      /* Cannot exec a shared library directly */
 #undef  EILSEQ
 #define EILSEQ          84      /* Illegal byte sequence */
 #undef  ERESTART
 #define ERESTART        85      /* Interrupted system call should be restarted */
 #undef  ESTRPIPE
 #define ESTRPIPE        86      /* Streams pipe error */
 #undef  EUSERS
 #define EUSERS          87      /* Too many users */
 #undef  ENOTSOCK
 #define ENOTSOCK        88      /* Socket operation on non-socket */
 #undef  EDESTADDRREQ
 #define EDESTADDRREQ    89      /* Destination address required */
 #undef  EMSGSIZE
 #define EMSGSIZE        90      /* Message too long */
 #undef  EPROTOTYPE
 #define EPROTOTYPE      91      /* Protocol wrong type for socket */
 #undef  ENOPROTOOPT
 #define ENOPROTOOPT     92      /* Protocol not available */
 #undef  EPROTONOSUPPORT
 #define EPROTONOSUPPORT 93      /* Protocol not supported */
 #undef  ESOCKTNOSUPPORT
 #define ESOCKTNOSUPPORT 94      /* Socket type not supported */
 #undef  EOPNOTSUPP
 #define EOPNOTSUPP      95      /* Operation not supported on transport endpoint */
 #undef  EPFNOSUPPORT
 #define EPFNOSUPPORT    96      /* Protocol family not supported */
 #undef  EAFNOSUPPORT
 #define EAFNOSUPPORT    97      /* Address family not supported by protocol */
 #undef  EADDRINUSE
 #define EADDRINUSE      98      /* Address already in use */
 #undef  EADDRNOTAVAIL
 #define EADDRNOTAVAIL   99      /* Cannot assign requested address */
 #undef  ENETDOWN
 #define ENETDOWN        100     /* Network is down */
 #undef  ENETUNREACH
 #define ENETUNREACH     101     /* Network is unreachable */
 #undef  ENETRESET
 #define ENETRESET       102     /* Network dropped connection because of reset */
 #undef  ECONNABORTED
 #define ECONNABORTED    103     /* Software caused connection abort */
 #undef  ECONNRESET
 #define ECONNRESET      104     /* Connection reset by peer */
 #undef  ENOBUFS
 #define ENOBUFS         105     /* No buffer space available */
 #undef  EISCONN
 #define EISCONN         106     /* Transport endpoint is already connected */
 #undef  ENOTCONN
 #define ENOTCONN        107     /* Transport endpoint is not connected */
 #undef  ESHUTDOWN
 #define ESHUTDOWN       108     /* Cannot send after transport endpoint shutdown */
 #undef  ETOOMANYREFS
 #define ETOOMANYREFS    109     /* Too many references: cannot splice */
 #undef  ETIMEDOUT
 #define ETIMEDOUT       110     /* Connection timed out */
 #undef  ECONNREFUSED
 #define ECONNREFUSED    111     /* Connection refused */
 #undef  EHOSTDOWN
 #define EHOSTDOWN       112     /* Host is down */
 #undef  EHOSTUNREACH
 #define EHOSTUNREACH    113     /* No route to host */
 #undef  EALREADY
 #define EALREADY        114     /* Operation already in progress */
 #undef  EINPROGRESS
 #define EINPROGRESS     115     /* Operation now in progress */
 #undef  ESTALE
 #define ESTALE          116     /* Stale NFS file handle */
 #undef  EUCLEAN
 #define EUCLEAN         117     /* Structure needs cleaning */
 #undef  ENOTNAM
 #define ENOTNAM         118     /* Not a XENIX named type file */
 #undef  ENAVAIL
 #define ENAVAIL         119     /* No XENIX semaphores available */
 #undef  EISNAM
 #define EISNAM          120     /* Is a named type file */
 #undef  EREMOTEIO
 #define EREMOTEIO       121     /* Remote I/O error */
 #undef  EDQUOT
 #define EDQUOT          122     /* Quota exceeded */
 #undef  ENOMEDIUM
 #define ENOMEDIUM       123     /* No medium found */
 #undef  EMEDIUMTYPE
 #define EMEDIUMTYPE     124     /* Wrong medium type */
 #undef  ECANCELED
 #define ECANCELED       125     /* Operation Canceled */
 #undef  ENOKEY
 #define ENOKEY          126     /* Required key not available */
 #undef  EKEYEXPIRED
 #define EKEYEXPIRED     127     /* Key has expired */
 #undef  EKEYREVOKED
 #define EKEYREVOKED     128     /* Key has been revoked */
 #undef  EKEYREJECTED
 #define EKEYREJECTED    129     /* Key was rejected by service */
 #undef  EOWNERDEAD
 #define EOWNERDEAD      130     /* Owner died */
 #undef  ENOTRECOVERABLE
 #define ENOTRECOVERABLE 131     /* State not recoverable */
 
 /* Missing stat.h defines.
  * The following are sys/stat.h definitions not currently present in the ARMCC
  * errno.h. Note, ARMCC errno.h defines some symbol values differing from
  * GCC_ARM/IAR/standard POSIX definitions. Guard against this and future
  * changes by changing the symbol definition for filesystem use.
  */
 #define     _IFMT   0170000 //< type of file
 #define     _IFSOCK 0140000 //< socket
 #define     _IFLNK  0120000 //< symbolic link
 #define     _IFREG  0100000 //< regular
 #define     _IFBLK  0060000 //< block special
 #define     _IFDIR  0040000 //< directory
 #define     _IFCHR  0020000 //< character special
 #define     _IFIFO  0010000 //< fifo special
 
 #define S_IFMT      _IFMT   //< type of file
 #define S_IFSOCK    _IFSOCK //< socket
 #define S_IFLNK     _IFLNK  //< symbolic link
 #define S_IFREG     _IFREG  //< regular
 #define S_IFBLK     _IFBLK  //< block special
 #define S_IFDIR     _IFDIR  //< directory
 #define S_IFCHR     _IFCHR  //< character special
 #define S_IFIFO     _IFIFO  //< fifo special
 
 #define S_IRWXU     (S_IRUSR | S_IWUSR | S_IXUSR)
 #define     S_IRUSR 0000400 ///< read permission, owner
 #define     S_IWUSR 0000200 ///< write permission, owner
 #define     S_IXUSR 0000100 ///< execute/search permission, owner
 #define S_IRWXG     (S_IRGRP | S_IWGRP | S_IXGRP)
 #define     S_IRGRP 0000040 ///< read permission, group
 #define     S_IWGRP 0000020 ///< write permission, group
 #define     S_IXGRP 0000010 ///< execute/search permission, group
 #define S_IRWXO     (S_IROTH | S_IWOTH | S_IXOTH)
 #define     S_IROTH 0000004 ///< read permission, other
 #define     S_IWOTH 0000002 ///< write permission, other
 #define     S_IXOTH 0000001 ///< execute/search permission, other
 
 /* Refer to sys/stat standard
  * Note: Not all fields may be supported by the underlying filesystem
  */
 struct stat {
     dev_t     st_dev;     ///< Device ID containing file
     ino_t     st_ino;     ///< File serial number
     mode_t    st_mode;    ///< Mode of file
     nlink_t   st_nlink;   ///< Number of links to file
 
     uid_t     st_uid;     ///< User ID
     gid_t     st_gid;     ///< Group ID
 
     off_t     st_size;    ///< Size of file in bytes
 
     time_t    st_atime;   ///< Time of last access
     time_t    st_mtime;   ///< Time of last data modification
     time_t    st_ctime;   ///< Time of last status change
 };
 
 struct statvfs {
     unsigned long  f_bsize;    ///< Filesystem block size
     unsigned long  f_frsize;   ///< Fragment size (block size)
 
     fsblkcnt_t     f_blocks;   ///< Number of blocks
     fsblkcnt_t     f_bfree;    ///< Number of free blocks
     fsblkcnt_t     f_bavail;   ///< Number of free blocks for unprivileged users
 
     unsigned long  f_fsid;     ///< Filesystem ID
 
     unsigned long  f_namemax;  ///< Maximum filename length
 };
 
 /* The following are dirent.h definitions are declared here to guarantee
  * consistency where structure may be different with different toolchains
  */
 struct dirent {
     char d_name[NAME_MAX + 1]; ///< Name of file
     uint8_t d_type;          ///< Type of file
 };
 
 enum {
     DT_UNKNOWN, ///< The file type could not be determined.
     DT_FIFO,    ///< This is a named pipe (FIFO).
     DT_CHR,     ///< This is a character device.
     DT_DIR,     ///< This is a directory.
     DT_BLK,     ///< This is a block device.
     DT_REG,     ///< This is a regular file.
     DT_LNK,     ///< This is a symbolic link.
     DT_SOCK,    ///< This is a UNIX domain socket.
 };
 
 /* fcntl.h defines */
 #define F_GETFL 3
 #define F_SETFL 4
 
 struct pollfd {
     int fd;
     short events;
     short revents;
 };
 
 /* POSIX-compatible I/O functions */
 #if __cplusplus
 extern "C" {
 #endif
     int open(const char *path, int oflag, ...);
 #ifndef __IAR_SYSTEMS_ICC__ /* IAR provides fdopen itself */
 #if __cplusplus
     std::FILE *fdopen(int fildes, const char *mode);
 #else
     FILE *fdopen(int fildes, const char *mode);
 #endif
 #endif
     ssize_t write(int fildes, const void *buf, size_t nbyte);
     ssize_t read(int fildes, void *buf, size_t nbyte);
     off_t lseek(int fildes, off_t offset, int whence);
     int ftruncate(int fildes, off_t length);
     int isatty(int fildes);
     int fsync(int fildes);
     int fstat(int fildes, struct stat *st);
     int fcntl(int fildes, int cmd, ...);
     int poll(struct pollfd fds[], nfds_t nfds, int timeout);
     int close(int fildes);
     int stat(const char *path, struct stat *st);
     int statvfs(const char *path, struct statvfs *buf);
     DIR *opendir(const char *);
     struct dirent *readdir(DIR *);
     int closedir(DIR *);
     void rewinddir(DIR *);
     long telldir(DIR *);
     void seekdir(DIR *, long);
     int mkdir(const char *name, mode_t n);
 #if __cplusplus
 }; // extern "C"
 
 namespace mbed {
 
 /** This call is an analogue to POSIX fdopen().
  *
  *  It associates a C stream to an already-opened FileHandle, to allow you to
  *  use C printf/scanf/fwrite etc. The provided FileHandle must remain open -
  *  it will be closed by the C library when fclose(FILE) is called.
  *
  *  The net effect is fdopen(bind_to_fd(fh), mode), with error handling.
  *
  *  @param fh       a pointer to an opened FileHandle
  *  @param mode     operation upon the file descriptor, e.g., "w+"
  *
  *  @returns        a pointer to FILE
  */
 std::FILE *fdopen(mbed::FileHandle *fh, const char *mode);
 
 /** Bind an mbed FileHandle to a POSIX file descriptor
  *
  * This is similar to fdopen, but only operating at the POSIX layer - it
  * associates a POSIX integer file descriptor with a FileHandle, to allow you
  * to use POSIX read/write calls etc. The provided FileHandle must remain open -
  * it will be closed when close(int) is called.
  *
  *  @param fh       a pointer to an opened FileHandle
  *
  *  @return         an integer file descriptor, or negative if no descriptors available
  */
 int bind_to_fd(mbed::FileHandle *fh);
 
 } // namespace mbed
 
 #endif // __cplusplus
 
 /**@}*/
 
 /**@}*/
 
 #endif /* RETARGET_H */
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