diff options
Diffstat (limited to 'libio/readline.c')
| -rw-r--r-- | libio/readline.c | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/libio/readline.c b/libio/readline.c new file mode 100644 index 0000000000..3638459176 --- /dev/null +++ b/libio/readline.c @@ -0,0 +1,170 @@ +/* fgets with ERANGE error reporting and size_t buffer length. + Copyright (C) 2017 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <http://www.gnu.org/licenses/>. */ + +#include <assert.h> +#include <errno.h> +#include <stdio.h> +#include <string.h> + +#include "libioP.h" + +/* Return -1 and set errno to EINVAL if it is ERANGE. */ +static ssize_t +fail_no_erange (void) +{ + if (errno == ERANGE) + __set_errno (EINVAL); + return -1; +} + +/* Slow path for reading the line. Called with no data in the stream + read buffer. Write data to [BUFFER, BUFFER_END). */ +static ssize_t +readline_slow (FILE *fp, char *buffer, char *buffer_end) +{ + char *start = buffer; + + while (buffer < buffer_end) + { + if (__underflow (fp) == EOF) + { + if (_IO_ferror_unlocked (fp)) + /* If the EOF was caused by a read error, report it. */ + return fail_no_erange (); + *buffer = '\0'; + /* Do not include the null terminator. */ + return buffer - start; + } + + /* __underflow has filled the buffer. */ + char *readptr = fp->_IO_read_ptr; + ssize_t readlen = fp->_IO_read_end - readptr; + /* Make sure that __underflow really has acquired some data. */ + assert (readlen > 0); + char *pnl = memchr (readptr, '\n', readlen); + if (pnl != NULL) + { + /* We found the terminator. */ + size_t line_length = pnl - readptr; + if (line_length + 2 > buffer_end - buffer) + /* Not enough room in the caller-supplied buffer. */ + break; + memcpy (buffer, readptr, line_length + 1); + buffer[line_length + 1] = '\0'; + fp->_IO_read_ptr = pnl + 1; + /* Do not include the null terminator. */ + return buffer - start + line_length + 1; + } + + if (readlen >= buffer_end - buffer) + /* Not enough room in the caller-supplied buffer. */ + break; + + /* Save and consume the stream buffer. */ + memcpy (buffer, readptr, readlen); + fp->_IO_read_ptr = fp->_IO_read_end; + buffer += readlen; + } + + /* The line does not fit into the buffer. */ + __set_errno (ERANGE); + return -1; +} + +ssize_t +__libc_readline_unlocked (FILE *fp, char *buffer, size_t buffer_length) +{ + char *buffer_end = buffer + buffer_length; + + /* Orient the stream. */ + if (__builtin_expect (fp->_mode, -1) == 0) + _IO_fwide (fp, -1); + + /* Fast path: The line terminator is found in the buffer. */ + char *readptr = fp->_IO_read_ptr; + ssize_t readlen = fp->_IO_read_end - readptr; + off64_t start_offset; /* File offset before reading anything. */ + if (readlen > 0) + { + char *pnl = memchr (readptr, '\n', readlen); + if (pnl != NULL) + { + size_t line_length = pnl - readptr; + /* Account for line and null terminators. */ + if (line_length + 2 > buffer_length) + { + __set_errno (ERANGE); + return -1; + } + memcpy (buffer, readptr, line_length + 1); + buffer[line_length + 1] = '\0'; + /* Consume the entire line. */ + fp->_IO_read_ptr = pnl + 1; + return line_length + 1; + } + + /* If the buffer does not have enough space for what is pending + in the stream (plus a NUL terminator), the buffer is too + small. */ + if (readlen + 1 > buffer_length) + { + __set_errno (ERANGE); + return -1; + } + + /* End of line not found. We need all the buffered data. Fall + through to the slow path. */ + memcpy (buffer, readptr, readlen); + buffer += readlen; + /* The original length is invalid after this point. Use + buffer_end instead. */ +#pragma GCC poison buffer_length + /* Read the old offset before updating the read pointer. */ + start_offset = __ftello64 (fp); + fp->_IO_read_ptr = fp->_IO_read_end; + } + else + { + readlen = 0; + start_offset = __ftello64 (fp); + } + + /* Slow path: Read more data from the underlying file. We need to + restore the file pointer if the buffer is too small. First, + check if the __ftello64 call above failed. */ + if (start_offset < 0) + return fail_no_erange (); + + ssize_t result = readline_slow (fp, buffer, buffer_end); + if (result < 0) + { + if (errno == ERANGE) + { + /* Restore the file pointer so that the caller may read the + same line again. */ + if (__fseeko64 (fp, start_offset, SEEK_SET) < 0) + return fail_no_erange (); + __set_errno (ERANGE); + } + /* Do not restore the file position on other errors; it is + likely that the __fseeko64 call would fail, too. */ + return -1; + } + return readlen + result; +} +libc_hidden_def (__libc_readline_unlocked) |