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Diffstat (limited to 'stdio/linewrap.c')
| -rw-r--r-- | stdio/linewrap.c | 353 |
1 files changed, 353 insertions, 0 deletions
diff --git a/stdio/linewrap.c b/stdio/linewrap.c new file mode 100644 index 0000000000..e821cc3575 --- /dev/null +++ b/stdio/linewrap.c @@ -0,0 +1,353 @@ +/* Word-wrapping and line-truncating streams. +Copyright (C) 1996 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 Library General Public License as +published by the Free Software Foundation; either version 2 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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. If +not, write to the Free Software Foundation, Inc., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + +#include <stdio.h> +#include <ctype.h> +#include <string.h> +#include <stdlib.h> + +/* We keep this data for each line-wrapping stream. */ + +struct data + { + const size_t *lmargin, *rmargin; /* Left and right margins. */ + const size_t *wrapmargin; /* Margin to wrap to, or null to truncate. */ + size_t point; /* Current column of last chars flushed. */ + + /* Original cookie and hooks from the stream. */ + void *cookie; + void (*output) (FILE *, int); + __io_close_fn *close; + __io_fileno_fn *fileno; + __io_seek_fn *seek; + }; + +/* Install our hooks into a stream. */ + +static inline void +wrap_stream (FILE *stream, struct data *d) +{ + static void lwoutput (FILE *, int); + static __io_close_fn lwclose; + static __io_fileno_fn lwfileno; + + stream->__cookie = d; + stream->__room_funcs.__output = &lwoutput; + stream->__io_funcs.__close = &lwclose; + stream->__io_funcs.__fileno = &lwfileno; + stream->__io_funcs.__seek = NULL; /* Cannot seek. */ +} + +/* Restore a stream to its original state. */ + +static inline void +unwrap_stream (FILE *stream, struct data *d) +{ + stream->__cookie = d->cookie; + stream->__room_funcs.__output = d->output; + stream->__io_funcs.__close = d->close; + stream->__io_funcs.__fileno = d->fileno; + stream->__io_funcs.__seek = d->seek; +} + +/* Cookie io functions that might get called on a wrapped stream. + Must pass the original cookie to the original functions. */ + +static int +lwclose (void *cookie) +{ + struct data *d = cookie; + return (*d->close) (d->cookie); +} + +static int +lwfileno (void *cookie) +{ + struct data *d = cookie; + return (*d->fileno) (d->cookie); +} + +/* This function is called when STREAM must be flushed. + C is EOF or a character to be appended to the buffer contents. */ + +static void +lwoutput (FILE *stream, int c) +{ + char *buf, *nl; + size_t len; + + /* Extract our data and restore the stream's original cookie + and output function so writes we do really go out. */ + struct data *d = stream->__cookie; + unwrap_stream (stream, d); + + /* Scan the buffer for newlines. */ + for (buf = stream->__buffer; + (buf < stream->__bufp || (c != EOF && c != '\n')) && !stream->__error) + { + size_t r; + + if (d->point == 0 && d->lmargin && *d->lmargin != 0) + { + /* We are starting a new line. Print spaces to the left margin. */ + const size_t pad = *d->lmargin; + if (stream->__bufp + pad < stream->__put_limit) + { + /* We can fit in them in the buffer by moving the + buffer text up and filling in the beginning. */ + memmove (buf + pad, buf, stream->__bufp - buf); + stream->__bufp += pad; /* Compensate for bigger buffer. */ + memset (buf, ' ', pad); /* Fill in the spaces. */ + buf += pad; /* Don't bother searching them. */ + } + else + { + /* No buffer space for spaces. Must flush. */ + size_t i; + char *olimit; + + len = stream->__bufp - buf; + olimit = stream->__put_limit; + stream->__bufp = stream->__put_limit = buf; + for (i = 0; i < pad; ++i) + (*d->output) (stream, ' '); + stream->__put_limit = olimit; + memcpy (stream->__bufp, buf, len); + stream->__bufp += len; + } + d->point = pad; + } + + len = stream->__bufp - buf; + nl = memchr (buf, '\n', len); + + if (!nl) + { + /* The buffer ends in a partial line. */ + + if (!d->rmargin || + d->point + len + (c != EOF && c != '\n') <= d->rmargin) + { + /* The remaining buffer text is a partial line and fits + within the maximum line width. Advance point for the + characters to be written and stop scanning. */ + d->point += len; + break; + } + else + /* Set the end-of-line pointer for the code below to + the end of the buffer. */ + nl = stream->__bufp; + } + else if (!d->rmargin || d->point + (nl - buf) <= d->rmargin) + { + /* The buffer contains a full line that fits within the maximum + line width. Reset point and scan the next line. */ + d->point = 0; + buf = nl + 1; + continue; + } + + /* This line is too long. */ + r = *d->rmargin; + + if (! d->wrapmargin) + { + /* Truncate the line by overwriting the excess with the + newline and anything after it in the buffer. */ + if (nl < stream->__bufp) + { + memcpy (buf + (r - d->point), nl, stream->__bufp - nl); + stream->__bufp -= buf + (r - d->point) - nl; + /* Reset point for the next line and start scanning it. */ + d->point = 0; + buf += r + 1; /* Skip full line plus \n. */ + } + else + { + /* The buffer ends with a partial line that is beyond the + maximum line width. Advance point for the characters + written, and discard those past the max from the buffer. */ + d->point += len; + stream->__bufp -= d->point - r; + if (c != '\n') + /* Swallow the extra character too. */ + c = EOF; + break; + } + } + else + { + /* Do word wrap. Go to the column just past the maximum line + width and scan back for the beginning of the word there. + Then insert a line break. */ + + char *p, *nextline; + int i; + + p = buf + (r + 1 - d->point); + while (p >= buf && !isblank (*p)) + --p; + nextline = p + 1; /* This will begin the next line. */ + + if (nextline > buf) + { + /* Swallow separating blanks. */ + do + --p; + while (isblank (*p)); + nl = p + 1; /* The newline will replace the first blank. */ + } + else + { + /* A single word that is greater than the maximum line width. + Oh well. Put it on an overlong line by itself. */ + p = buf + (r + 1 - d->point); + /* Find the end of the long word. */ + do + ++p; + while (p < nl && !isblank (*p)); + if (p == nl) + { + /* It already ends a line. No fussing required. */ + d->point = 0; + buf = nl + 1; + continue; + } + /* We will move the newline to replace the first blank. */ + nl = p; + /* Swallow separating blanks. */ + do + ++p; + while (isblank (*p)); + /* The next line will start here. */ + nextline = p; + } + + /* Temporarily reset bufp to include just the first line. */ + stream->__bufp = nl; + if (nextline - (nl + 1) < d->wrap) + /* The margin needs more blanks than we removed. + Output the first line so we can use the space. */ + (*d->output) (stream, '\n'); + else + /* We can fit the newline and blanks in before + the next word. */ + *stream->__bufp++ = '\n'; + + /* Reset the counter of what has been output this line. */ + d->point = 0; + + /* Add blanks up to the wrap margin column. */ + for (i = 0; i < d->wrap; ++i) + *stream->__bufp++ = ' '; + + /* Copy the tail of the original buffer into the current buffer + position. */ + if (stream->__bufp != nextline) + memcpy (stream->__bufp, nextline, buf + len - nextline); + len -= nextline - buf; + + /* Continue the scan on the remaining lines in the buffer. */ + buf = stream->__bufp; + + /* Restore bufp to include all the remaining text. */ + stream->__bufp += len; + } + } + + if (!stream->__error) + { + (*d->output) (stream, c); + if (c == '\n') + d->point = 0; + else if (c != EOF) + ++d->point; + } + + wrap_stream (stream, d); +} + +/* Modify STREAM so that it prefixes lines written on it with *LMARGIN + spaces and limits them to *RMARGIN columns total. If WRAP is not null, + words that extend past *RMARGIN are wrapped by replacing the whitespace + before them with a newline and *WRAP spaces. Otherwise, chars beyond + *RMARGIN are simply dropped until a newline. Returns STREAM after + modifying it, or NULL if there was an error. The pointers passed are + stored in the stream and so must remain valid until `line_unwrap_stream' + is called; the values pointed to can be changed between stdio calls. */ + +FILE * +line_wrap_stream (FILE *stream, size_t *lmargin, size_t *rmargin, size_t *wrap) +{ + struct data *d = malloc (sizeof *d); + + if (!d) + return NULL; + + /* Ensure full setup before we start tweaking. */ + fflush (stream); + + /* Initialize our wrapping state. */ + d->point = 0; + + /* Save the original cookie and output and close hooks. */ + d->cookie = stream->__cookie; + d->output = stream->__room_funcs.__output; + d->close = stream->__io_funcs.__close; + d->fileno = stream->__io_funcs.__fileno; + + /* Take over the stream. */ + wrap_stream (stream, d); + + /* Line-wrapping streams are normally line-buffered. This is not + required, just assumed desired. The wrapping feature should continue + to work if the stream is switched to full or no buffering. */ + stream->__linebuf = 1; + +#define ref(arg) d->arg = arg + ref (lmargin); + ref (rmargin); + ref (wrap); +#undef ref + + return stream; +} + +/* Remove the hooks placed in STREAM by `line_wrap_stream'. */ + +void +line_unwrap_stream (FILE *stream) +{ + struct data *d = stream->__cookie; + unwrap_stream (stream, d); + free (d); +} + +#ifdef TEST +int +main (int argc, char **argv) +{ + int c; + puts ("stopme"); + line_wrap_stream (stdout, atoi (argv[1]), atoi (argv[2] ?: "-1")); + while ((c = getchar()) != EOF) putchar (c); + return 0; +} +#endif |