/**************************************************************************** * libs/libc/stdio/lib_libfread.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 #include #include #include #include #include #include "libc.h" /**************************************************************************** * Public Functions ****************************************************************************/ /**************************************************************************** * Name: lib_fread ****************************************************************************/ ssize_t lib_fread(FAR void *ptr, size_t count, FAR FILE *stream) { FAR unsigned char *dest = (FAR unsigned char *)ptr; ssize_t bytes_read; size_t remaining = count; #ifndef CONFIG_STDIO_DISABLE_BUFFERING int ret; #endif /* Make sure that reading from this stream is allowed */ if (!stream || (stream->fs_oflags & O_RDOK) == 0) { set_errno(EBADF); } else { /* The stream must be stable until we complete the read */ lib_take_semaphore(stream); #if CONFIG_NUNGET_CHARS > 0 /* First, re-read any previously ungotten characters */ while (stream->fs_nungotten > 0 && remaining > 0) { /* Decrement the count of ungotten bytes to get an index */ stream->fs_nungotten--; /* Return the last ungotten byte */ *dest++ = stream->fs_ungotten[stream->fs_nungotten]; /* That's one less byte that we have to read */ remaining--; } #endif #ifndef CONFIG_STDIO_DISABLE_BUFFERING /* Is there an I/O buffer? */ if (stream->fs_bufstart != NULL) { /* If the buffer is currently being used for write access, then * flush all of the buffered write data. We do not support * concurrent buffered read/write access. */ ret = lib_wrflush(stream); if (ret < 0) { lib_give_semaphore(stream); return ret; } /* Now get any other needed chars from the buffer or the file. */ while (remaining > 0) { /* Is there readable data in the buffer? */ while (remaining > 0 && stream->fs_bufpos < stream->fs_bufread) { /* Yes, copy a byte into the user buffer */ *dest++ = *stream->fs_bufpos++; remaining--; } /* The buffer is empty OR we have already supplied the number * of bytes requested in the read. Check if we need to read * more from the file. */ if (remaining > 0) { size_t buffer_available; /* We need to read more data into the buffer from the * file */ /* Mark the buffer empty */ stream->fs_bufpos = stream->fs_bufread = stream->fs_bufstart; /* How much space is available in the buffer? */ buffer_available = stream->fs_bufend - stream->fs_bufread; /* Will the number of bytes that we need to read fit into * the buffer space that is available? If the read size is * larger than the buffer, then read some of the data * directly into the user's buffer. */ if (remaining > buffer_available) { bytes_read = _NX_READ(stream->fs_fd, dest, remaining); if (bytes_read < 0) { /* An error occurred on the read. */ _NX_SETERRNO(bytes_read); goto errout_with_errno; } else if (bytes_read == 0) { /* We are at the end of the file. But we may * already have buffered data. In that case, * we will report the EOF indication later. */ goto shortread; } else { /* Some (perhaps all) bytes were read. Adjust the * dest pointer and remaining bytes to be read. */ DEBUGASSERT(bytes_read <= remaining); dest += bytes_read; remaining -= bytes_read; } } else { /* The number of bytes required to satisfy the read * is less than or equal to the size of the buffer * space that we have left. Read as much as we can * into the buffer. */ bytes_read = _NX_READ(stream->fs_fd, stream->fs_bufread, buffer_available); if (bytes_read < 0) { /* An error occurred on the read. The error code * is in the 'errno' variable. */ _NX_SETERRNO(bytes_read); goto errout_with_errno; } else if (bytes_read == 0) { /* We are at the end of the file. But we may * already have buffered data. In that case, * we will report the EOF indication later. */ goto shortread; } else { /* Some (perhaps all) bytes were read */ stream->fs_bufread += bytes_read; } } } } } else #endif { /* Now get any other needed chars from the file. */ while (remaining > 0) { bytes_read = _NX_READ(stream->fs_fd, dest, remaining); if (bytes_read < 0) { /* An error occurred on the read. The error code is * in the 'errno' variable. */ _NX_SETERRNO(bytes_read); goto errout_with_errno; } else if (bytes_read == 0) { /* We are at the end of the file. But we may already * have buffered data. In that case, we will report * the EOF indication later. */ break; } else { DEBUGASSERT(bytes_read <= remaining); dest += bytes_read; remaining -= bytes_read; } } } #ifndef CONFIG_STDIO_DISABLE_BUFFERING /* Here after a successful (but perhaps short) read. A short read can * only occur is read() returns 0 (end-of-file). */ shortread: #endif /* Set or clear the EOF indicator. If we get here because of a * short read and the total number of bytes read is zero, then * we must be at the end-of-file. */ if (remaining == 0) { stream->fs_flags &= ~__FS_FLAG_EOF; } else { stream->fs_flags |= __FS_FLAG_EOF; } lib_give_semaphore(stream); } return count - remaining; /* Error exits */ errout_with_errno: stream->fs_flags |= __FS_FLAG_ERROR; lib_give_semaphore(stream); return -get_errno(); }