source: trunk/third/openssh/buffer.c @ 19827

/*
 * Author: Tatu Ylonen <ylo@cs.hut.fi>
 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
 *                    All rights reserved
 * Functions for manipulating fifo buffers (that can grow if needed).
 *
 * As far as I am concerned, the code I have written for this software
 * can be used freely for any purpose.  Any derived versions of this
 * software must be clearly marked as such, and if the derived work is
 * incompatible with the protocol description in the RFC file, it must be
 * called by a name other than "ssh" or "Secure Shell".
 */

#include "includes.h"
RCSID("$OpenBSD: buffer.c,v 1.16 2002/06/26 08:54:18 markus Exp $");

#include "xmalloc.h"
#include "buffer.h"
#include "log.h"

/* Initializes the buffer structure. */

void
buffer_init(Buffer *buffer)
{
        const u_int len = 4096;

        buffer->alloc = 0;
        buffer->buf = xmalloc(len);
        buffer->alloc = len;
        buffer->offset = 0;
        buffer->end = 0;
}

/* Frees any memory used for the buffer. */

void
buffer_free(Buffer *buffer)
{
        if (buffer->alloc > 0) {
                memset(buffer->buf, 0, buffer->alloc);
                xfree(buffer->buf);
        }
}

/*
 * Clears any data from the buffer, making it empty.  This does not actually
 * zero the memory.
 */

void
buffer_clear(Buffer *buffer)
{
        buffer->offset = 0;
        buffer->end = 0;
}

/* Appends data to the buffer, expanding it if necessary. */

void
buffer_append(Buffer *buffer, const void *data, u_int len)
{
        void *p;
        p = buffer_append_space(buffer, len);
        memcpy(p, data, len);
}

/*
 * Appends space to the buffer, expanding the buffer if necessary. This does
 * not actually copy the data into the buffer, but instead returns a pointer
 * to the allocated region.
 */

void *
buffer_append_space(Buffer *buffer, u_int len)
{
        u_int newlen;
        void *p;

        if (len > 0x100000)
                fatal("buffer_append_space: len %u not supported", len);

        /* If the buffer is empty, start using it from the beginning. */
        if (buffer->offset == buffer->end) {
                buffer->offset = 0;
                buffer->end = 0;
        }
restart:
        /* If there is enough space to store all data, store it now. */
        if (buffer->end + len < buffer->alloc) {
                p = buffer->buf + buffer->end;
                buffer->end += len;
                return p;
        }
        /*
         * If the buffer is quite empty, but all data is at the end, move the
         * data to the beginning and retry.
         */
        if (buffer->offset > buffer->alloc / 2) {
                memmove(buffer->buf, buffer->buf + buffer->offset,
                        buffer->end - buffer->offset);
                buffer->end -= buffer->offset;
                buffer->offset = 0;
                goto restart;
        }
        /* Increase the size of the buffer and retry. */
        
        newlen = buffer->alloc + len + 32768;
        if (newlen > 0xa00000)
                fatal("buffer_append_space: alloc %u not supported",
                    newlen);
        buffer->buf = xrealloc(buffer->buf, newlen);
        buffer->alloc = newlen;
        goto restart;
        /* NOTREACHED */
}

/* Returns the number of bytes of data in the buffer. */

u_int
buffer_len(Buffer *buffer)
{
        return buffer->end - buffer->offset;
}

/* Gets data from the beginning of the buffer. */

void
buffer_get(Buffer *buffer, void *buf, u_int len)
{
        if (len > buffer->end - buffer->offset)
                fatal("buffer_get: trying to get more bytes %d than in buffer %d",
                    len, buffer->end - buffer->offset);
        memcpy(buf, buffer->buf + buffer->offset, len);
        buffer->offset += len;
}

/* Consumes the given number of bytes from the beginning of the buffer. */

void
buffer_consume(Buffer *buffer, u_int bytes)
{
        if (bytes > buffer->end - buffer->offset)
                fatal("buffer_consume: trying to get more bytes than in buffer");
        buffer->offset += bytes;
}

/* Consumes the given number of bytes from the end of the buffer. */

void
buffer_consume_end(Buffer *buffer, u_int bytes)
{
        if (bytes > buffer->end - buffer->offset)
                fatal("buffer_consume_end: trying to get more bytes than in buffer");
        buffer->end -= bytes;
}

/* Returns a pointer to the first used byte in the buffer. */

void *
buffer_ptr(Buffer *buffer)
{
        return buffer->buf + buffer->offset;
}

/* Dumps the contents of the buffer to stderr. */

void
buffer_dump(Buffer *buffer)
{
        int i;
        u_char *ucp = buffer->buf;

        for (i = buffer->offset; i < buffer->end; i++) {
                fprintf(stderr, "%02x", ucp[i]);
                if ((i-buffer->offset)%16==15)
                        fprintf(stderr, "\r\n");
                else if ((i-buffer->offset)%2==1)
                        fprintf(stderr, " ");
        }
        fprintf(stderr, "\r\n");
}