mirror_frr/lib/buffer.c

/*
 * Buffering of output and input.
 * Copyright (C) 1998 Kunihiro Ishiguro
 *
 * This file is part of GNU Zebra.
 *
 * GNU Zebra is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published
 * by the Free Software Foundation; either version 2, or (at your
 * option) any later version.
 *
 * GNU Zebra 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
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <zebra.h>

#include "memory.h"
#include "buffer.h"
#include "log.h"
#include "network.h"
#include "lib_errors.h"

#include <stddef.h>

DEFINE_MTYPE_STATIC(LIB, BUFFER, "Buffer")
DEFINE_MTYPE_STATIC(LIB, BUFFER_DATA, "Buffer data")

/* Buffer master. */
struct buffer {
	/* Data list. */
	struct buffer_data *head;
	struct buffer_data *tail;

	/* Size of each buffer_data chunk. */
	size_t size;
};

/* Data container. */
struct buffer_data {
	struct buffer_data *next;

	/* Location to add new data. */
	size_t cp;

	/* Pointer to data not yet flushed. */
	size_t sp;

	/* Actual data stream (variable length). */
	unsigned char data[]; /* real dimension is buffer->size */
};

/* It should always be true that: 0 <= sp <= cp <= size */

/* Default buffer size (used if none specified).  It is rounded up to the
   next page boundery. */
#define BUFFER_SIZE_DEFAULT		4096

#define BUFFER_DATA_FREE(D) XFREE(MTYPE_BUFFER_DATA, (D))

/* Make new buffer. */
struct buffer *buffer_new(size_t size)
{
	struct buffer *b;

	b = XCALLOC(MTYPE_BUFFER, sizeof(struct buffer));

	if (size)
		b->size = size;
	else {
		static size_t default_size;
		if (!default_size) {
			long pgsz = sysconf(_SC_PAGESIZE);
			default_size = ((((BUFFER_SIZE_DEFAULT - 1) / pgsz) + 1)
					* pgsz);
		}
		b->size = default_size;
	}

	return b;
}

/* Free buffer. */
void buffer_free(struct buffer *b)
{
	buffer_reset(b);
	XFREE(MTYPE_BUFFER, b);
}

/* Make string clone. */
char *buffer_getstr(struct buffer *b)
{
	size_t totlen = 0;
	struct buffer_data *data;
	char *s;
	char *p;

	for (data = b->head; data; data = data->next)
		totlen += data->cp - data->sp;
	if (!(s = XMALLOC(MTYPE_TMP, totlen + 1)))
		return NULL;
	p = s;
	for (data = b->head; data; data = data->next) {
		memcpy(p, data->data + data->sp, data->cp - data->sp);
		p += data->cp - data->sp;
	}
	*p = '\0';
	return s;
}

/* Return 1 if buffer is empty. */
int buffer_empty(struct buffer *b)
{
	return (b->head == NULL);
}

/* Clear and free all allocated data. */
void buffer_reset(struct buffer *b)
{
	struct buffer_data *data;
	struct buffer_data *next;

	for (data = b->head; data; data = next) {
		next = data->next;
		BUFFER_DATA_FREE(data);
	}
	b->head = b->tail = NULL;
}

/* Add buffer_data to the end of buffer. */
static struct buffer_data *buffer_add(struct buffer *b)
{
	struct buffer_data *d;

	d = XMALLOC(MTYPE_BUFFER_DATA,
		    offsetof(struct buffer_data, data) + b->size);
	d->cp = d->sp = 0;
	d->next = NULL;

	if (b->tail)
		b->tail->next = d;
	else
		b->head = d;
	b->tail = d;

	return d;
}

/* Write data to buffer. */
void buffer_put(struct buffer *b, const void *p, size_t size)
{
	struct buffer_data *data = b->tail;
	const char *ptr = p;

	/* We use even last one byte of data buffer. */
	while (size) {
		size_t chunk;

		/* If there is no data buffer add it. */
		if (data == NULL || data->cp == b->size)
			data = buffer_add(b);

		chunk = ((size <= (b->size - data->cp)) ? size
							: (b->size - data->cp));
		memcpy((data->data + data->cp), ptr, chunk);
		size -= chunk;
		ptr += chunk;
		data->cp += chunk;
	}
}

/* Insert character into the buffer. */
void buffer_putc(struct buffer *b, uint8_t c)
{
	buffer_put(b, &c, 1);
}

/* Put string to the buffer. */
void buffer_putstr(struct buffer *b, const char *c)
{
	buffer_put(b, c, strlen(c));
}

/* Expand \n to \r\n */
void buffer_put_crlf(struct buffer *b, const void *origp, size_t origsize)
{
	struct buffer_data *data = b->tail;
	const char *p = origp, *end = p + origsize, *lf;
	size_t size;

	lf = memchr(p, '\n', end - p);

	/* We use even last one byte of data buffer. */
	while (p < end) {
		size_t avail, chunk;

		/* If there is no data buffer add it. */
		if (data == NULL || data->cp == b->size)
			data = buffer_add(b);

		size = (lf ? lf : end) - p;
		avail = b->size - data->cp;

		chunk = (size <= avail) ? size : avail;
		memcpy(data->data + data->cp, p, chunk);

		p += chunk;
		data->cp += chunk;

		if (lf && size <= avail) {
			/* we just copied up to (including) a '\n' */
			if (data->cp == b->size)
				data = buffer_add(b);
			data->data[data->cp++] = '\r';
			if (data->cp == b->size)
				data = buffer_add(b);
			data->data[data->cp++] = '\n';

			p++;
			lf = memchr(p, '\n', end - p);
		}
	}
}

/* Keep flushing data to the fd until the buffer is empty or an error is
   encountered or the operation would block. */
buffer_status_t buffer_flush_all(struct buffer *b, int fd)
{
	buffer_status_t ret;
	struct buffer_data *head;
	size_t head_sp;

	if (!b->head)
		return BUFFER_EMPTY;
	head_sp = (head = b->head)->sp;
	/* Flush all data. */
	while ((ret = buffer_flush_available(b, fd)) == BUFFER_PENDING) {
		if ((b->head == head) && (head_sp == head->sp)
		    && (errno != EINTR))
			/* No data was flushed, so kernel buffer must be full.
			 */
			return ret;
		head_sp = (head = b->head)->sp;
	}

	return ret;
}

/* Flush enough data to fill a terminal window of the given scene (used only
   by vty telnet interface). */
buffer_status_t buffer_flush_window(struct buffer *b, int fd, int width,
				    int height, int erase_flag,
				    int no_more_flag)
{
	int nbytes;
	int iov_alloc;
	int iov_index;
	struct iovec *iov;
	struct iovec small_iov[3];
	char more[] = " --More-- ";
	char erase[] = {0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08, 0x08,
			0x08, 0x08, ' ',  ' ',  ' ',  ' ',  ' ',  ' ',
			' ',  ' ',  ' ',  ' ',  0x08, 0x08, 0x08, 0x08,
			0x08, 0x08, 0x08, 0x08, 0x08, 0x08};
	struct buffer_data *data;
	int column;

	if (!b->head)
		return BUFFER_EMPTY;

	if (height < 1)
		height = 1;
	else if (height >= 2)
		height--;
	if (width < 1)
		width = 1;

	/* For erase and more data add two to b's buffer_data count.*/
	if (b->head->next == NULL) {
		iov_alloc = array_size(small_iov);
		iov = small_iov;
	} else {
		iov_alloc = ((height * (width + 2)) / b->size) + 10;
		iov = XMALLOC(MTYPE_TMP, iov_alloc * sizeof(*iov));
	}
	iov_index = 0;

	/* Previously print out is performed. */
	if (erase_flag) {
		iov[iov_index].iov_base = erase;
		iov[iov_index].iov_len = sizeof erase;
		iov_index++;
	}

	/* Output data. */
	column = 1; /* Column position of next character displayed. */
	for (data = b->head; data && (height > 0); data = data->next) {
		size_t cp;

		cp = data->sp;
		while ((cp < data->cp) && (height > 0)) {
			/* Calculate lines remaining and column position after
			   displaying
			   this character. */
			if (data->data[cp] == '\r')
				column = 1;
			else if ((data->data[cp] == '\n')
				 || (column == width)) {
				column = 1;
				height--;
			} else
				column++;
			cp++;
		}
		iov[iov_index].iov_base = (char *)(data->data + data->sp);
		iov[iov_index++].iov_len = cp - data->sp;
		data->sp = cp;

		if (iov_index == iov_alloc)
		/* This should not ordinarily happen. */
		{
			iov_alloc *= 2;
			if (iov != small_iov) {
				iov = XREALLOC(MTYPE_TMP, iov,
					       iov_alloc * sizeof(*iov));
			} else {
				/* This should absolutely never occur. */
				flog_err_sys(
					LIB_ERR_SYSTEM_CALL,
					"%s: corruption detected: iov_small overflowed; "
					"head %p, tail %p, head->next %p",
					__func__, (void *)b->head,
					(void *)b->tail, (void *)b->head->next);
				iov = XMALLOC(MTYPE_TMP,
					      iov_alloc * sizeof(*iov));
				memcpy(iov, small_iov, sizeof(small_iov));
			}
		}
	}

	/* In case of `more' display need. */
	if (b->tail && (b->tail->sp < b->tail->cp) && !no_more_flag) {
		iov[iov_index].iov_base = more;
		iov[iov_index].iov_len = sizeof more;
		iov_index++;
	}


#ifdef IOV_MAX
	/* IOV_MAX are normally defined in <sys/uio.h> , Posix.1g.
	   example: Solaris2.6 are defined IOV_MAX size at 16.     */
	{
		struct iovec *c_iov = iov;
		nbytes = 0; /* Make sure it's initialized. */

		while (iov_index > 0) {
			int iov_size;

			iov_size =
				((iov_index > IOV_MAX) ? IOV_MAX : iov_index);
			if ((nbytes = writev(fd, c_iov, iov_size)) < 0) {
				zlog_warn("%s: writev to fd %d failed: %s",
					  __func__, fd, safe_strerror(errno));
				break;
			}

			/* move pointer io-vector */
			c_iov += iov_size;
			iov_index -= iov_size;
		}
	}
#else  /* IOV_MAX */
	if ((nbytes = writev(fd, iov, iov_index)) < 0)
		zlog_warn("%s: writev to fd %d failed: %s", __func__, fd,
			  safe_strerror(errno));
#endif /* IOV_MAX */

	/* Free printed buffer data. */
	while (b->head && (b->head->sp == b->head->cp)) {
		struct buffer_data *del;
		if (!(b->head = (del = b->head)->next))
			b->tail = NULL;
		BUFFER_DATA_FREE(del);
	}

	if (iov != small_iov)
		XFREE(MTYPE_TMP, iov);

	return (nbytes < 0) ? BUFFER_ERROR
			    : (b->head ? BUFFER_PENDING : BUFFER_EMPTY);
}

/* This function (unlike other buffer_flush* functions above) is designed
to work with non-blocking sockets.  It does not attempt to write out
all of the queued data, just a "big" chunk.  It returns 0 if it was
able to empty out the buffers completely, 1 if more flushing is
required later, or -1 on a fatal write error. */
buffer_status_t buffer_flush_available(struct buffer *b, int fd)
{

/* These are just reasonable values to make sure a significant amount of
data is written.  There's no need to go crazy and try to write it all
in one shot. */
#ifdef IOV_MAX
#define MAX_CHUNKS ((IOV_MAX >= 16) ? 16 : IOV_MAX)
#else
#define MAX_CHUNKS 16
#endif
#define MAX_FLUSH 131072

	struct buffer_data *d;
	size_t written;
	struct iovec iov[MAX_CHUNKS];
	size_t iovcnt = 0;
	size_t nbyte = 0;

	if (fd < 0)
		return BUFFER_ERROR;

	for (d = b->head; d && (iovcnt < MAX_CHUNKS) && (nbyte < MAX_FLUSH);
	     d = d->next, iovcnt++) {
		iov[iovcnt].iov_base = d->data + d->sp;
		nbyte += (iov[iovcnt].iov_len = d->cp - d->sp);
	}

	if (!nbyte)
		/* No data to flush: should we issue a warning message? */
		return BUFFER_EMPTY;

	/* only place where written should be sign compared */
	if ((ssize_t)(written = writev(fd, iov, iovcnt)) < 0) {
		if (ERRNO_IO_RETRY(errno))
			/* Calling code should try again later. */
			return BUFFER_PENDING;
		zlog_warn("%s: write error on fd %d: %s", __func__, fd,
			  safe_strerror(errno));
		return BUFFER_ERROR;
	}

	/* Free printed buffer data. */
	while (written > 0) {
		struct buffer_data *d;
		if (!(d = b->head)) {
			flog_err(
				LIB_ERR_DEVELOPMENT,
				"%s: corruption detected: buffer queue empty, but written is %lu",
				__func__, (unsigned long)written);
			break;
		}
		if (written < d->cp - d->sp) {
			d->sp += written;
			return BUFFER_PENDING;
		}

		written -= (d->cp - d->sp);
		if (!(b->head = d->next))
			b->tail = NULL;
		BUFFER_DATA_FREE(d);
	}

	return b->head ? BUFFER_PENDING : BUFFER_EMPTY;

#undef MAX_CHUNKS
#undef MAX_FLUSH
}

buffer_status_t buffer_write(struct buffer *b, int fd, const void *p,
			     size_t size)
{
	ssize_t nbytes;

#if 0
	/*
	 * Should we attempt to drain any previously buffered data?
	 * This could help reduce latency in pushing out the data if
	 * we are stuck in a long-running thread that is preventing
	 * the main select loop from calling the flush thread...
	 */
	if (b->head && (buffer_flush_available(b, fd) == BUFFER_ERROR))
		return BUFFER_ERROR;
#endif
	if (b->head)
		/* Buffer is not empty, so do not attempt to write the new data.
		 */
		nbytes = 0;
	else if ((nbytes = write(fd, p, size)) < 0) {
		if (ERRNO_IO_RETRY(errno))
			nbytes = 0;
		else {
			zlog_warn("%s: write error on fd %d: %s", __func__, fd,
				  safe_strerror(errno));
			return BUFFER_ERROR;
		}
	}
	/* Add any remaining data to the buffer. */
	{
		size_t written = nbytes;
		if (written < size)
			buffer_put(b, ((const char *)p) + written,
				   size - written);
	}
	return b->head ? BUFFER_PENDING : BUFFER_EMPTY;
}