/*      $OpenBSD: buffer.c,v 1.33 2022/12/27 23:05:55 jmc Exp $ */

/*
 * Copyright (c) 2002, 2003 Niels Provos <provos@citi.umich.edu>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/time.h>
#include <sys/ioctl.h>

#include <assert.h>
#include <errno.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <unistd.h>

#include "event.h"
#include "log.h"

struct evbuffer *
evbuffer_new(void)
{
        struct evbuffer *buffer;

        buffer = calloc(1, sizeof(struct evbuffer));

        return (buffer);
}

void
evbuffer_free(struct evbuffer *buffer)
{
        free(buffer->orig_buffer);
        free(buffer);
}

/*
 * This is a destructive add.  The data from one buffer moves into
 * the other buffer.
 */

#define SWAP(x,y) do { \
        (x)->buffer = (y)->buffer; \
        (x)->orig_buffer = (y)->orig_buffer; \
        (x)->misalign = (y)->misalign; \
        (x)->totallen = (y)->totallen; \
        (x)->off = (y)->off; \
} while (0)

int
evbuffer_add_buffer(struct evbuffer *outbuf, struct evbuffer *inbuf)
{
        int res;

        /* Short cut for better performance */
        if (outbuf->off == 0) {
                struct evbuffer tmp;
                size_t oldoff = inbuf->off;

                /* Swap them directly */
                SWAP(&tmp, outbuf);
                SWAP(outbuf, inbuf);
                SWAP(inbuf, &tmp);

                /*
                 * Optimization comes with a price; we need to notify the
                 * buffer if necessary of the changes. oldoff is the amount
                 * of data that we transferred from inbuf to outbuf
                 */
                if (inbuf->off != oldoff && inbuf->cb != NULL)
                        (*inbuf->cb)(inbuf, oldoff, inbuf->off, inbuf->cbarg);
                if (oldoff && outbuf->cb != NULL)
                        (*outbuf->cb)(outbuf, 0, oldoff, outbuf->cbarg);

                return (0);
        }

        res = evbuffer_add(outbuf, inbuf->buffer, inbuf->off);
        if (res == 0) {
                /* We drain the input buffer on success */
                evbuffer_drain(inbuf, inbuf->off);
        }

        return (res);
}

int
evbuffer_add_vprintf(struct evbuffer *buf, const char *fmt, va_list ap)
{
        char *buffer;
        size_t space;
        size_t oldoff = buf->off;
        int sz;
        va_list aq;

        /* make sure that at least some space is available */
        if (evbuffer_expand(buf, 64) < 0)
                return (-1);
        for (;;) {
                size_t used = buf->misalign + buf->off;
                buffer = (char *)buf->buffer + buf->off;
                assert(buf->totallen >= used);
                space = buf->totallen - used;

                va_copy(aq, ap);

                sz = vsnprintf(buffer, space, fmt, aq);

                va_end(aq);

                if (sz < 0)
                        return (-1);
                if ((size_t)sz < space) {
                        buf->off += sz;
                        if (buf->cb != NULL)
                                (*buf->cb)(buf, oldoff, buf->off, buf->cbarg);
                        return (sz);
                }
                if (evbuffer_expand(buf, sz + 1) == -1)
                        return (-1);

        }
        /* NOTREACHED */
}

int
evbuffer_add_printf(struct evbuffer *buf, const char *fmt, ...)
{
        int res = -1;
        va_list ap;

        va_start(ap, fmt);
        res = evbuffer_add_vprintf(buf, fmt, ap);
        va_end(ap);

        return (res);
}

/* Reads data from an event buffer and drains the bytes read */

int
evbuffer_remove(struct evbuffer *buf, void *data, size_t datlen)
{
        size_t nread = datlen;
        if (nread >= buf->off)
                nread = buf->off;

        memcpy(data, buf->buffer, nread);
        evbuffer_drain(buf, nread);

        return (nread);
}

/*
 * Reads a line terminated by either '\r\n', '\n\r' or '\r' or '\n'.
 * The returned buffer needs to be freed by the called.
 */

char *
evbuffer_readline(struct evbuffer *buffer)
{
        u_char *data = EVBUFFER_DATA(buffer);
        size_t len = EVBUFFER_LENGTH(buffer);
        char *line;
        size_t i;

        for (i = 0; i < len; i++) {
                if (data[i] == '\r' || data[i] == '\n')
                        break;
        }

        if (i == len)
                return (NULL);

        if ((line = malloc(i + 1)) == NULL) {
                event_warn("%s: out of memory", __func__);
                return (NULL);
        }

        memcpy(line, data, i);
        line[i] = '\0';

        /*
         * Some protocols terminate a line with '\r\n', so check for
         * that, too.
         */
        if ( i < len - 1 ) {
                char fch = data[i], sch = data[i+1];

                /* Drain one more character if needed */
                if ( (sch == '\r' || sch == '\n') && sch != fch )
                        i += 1;
        }

        evbuffer_drain(buffer, i + 1);

        return (line);
}


char *
evbuffer_readln(struct evbuffer *buffer, size_t *n_read_out,
                enum evbuffer_eol_style eol_style)
{
        u_char *data = EVBUFFER_DATA(buffer);
        u_char *start_of_eol, *end_of_eol;
        size_t len = EVBUFFER_LENGTH(buffer);
        char *line;
        size_t i, n_to_copy, n_to_drain;

        if (n_read_out)
                *n_read_out = 0;

        /* depending on eol_style, set start_of_eol to the first character
         * in the newline, and end_of_eol to one after the last character. */
        switch (eol_style) {
        case EVBUFFER_EOL_ANY:
                for (i = 0; i < len; i++) {
                        if (data[i] == '\r' || data[i] == '\n')
                                break;
                }
                if (i == len)
                        return (NULL);
                start_of_eol = data+i;
                ++i;
                for ( ; i < len; i++) {
                        if (data[i] != '\r' && data[i] != '\n')
                                break;
                }
                end_of_eol = data+i;
                break;
        case EVBUFFER_EOL_CRLF:
                end_of_eol = memchr(data, '\n', len);
                if (!end_of_eol)
                        return (NULL);
                if (end_of_eol > data && *(end_of_eol-1) == '\r')
                        start_of_eol = end_of_eol - 1;
                else
                        start_of_eol = end_of_eol;
                end_of_eol++; /*point to one after the LF. */
                break;
        case EVBUFFER_EOL_CRLF_STRICT: {
                u_char *cp = data;
                while ((cp = memchr(cp, '\r', len-(cp-data)))) {
                        if (cp < data+len-1 && *(cp+1) == '\n')
                                break;
                        if (++cp >= data+len) {
                                cp = NULL;
                                break;
                        }
                }
                if (!cp)
                        return (NULL);
                start_of_eol = cp;
                end_of_eol = cp+2;
                break;
        }
        case EVBUFFER_EOL_LF:
                start_of_eol = memchr(data, '\n', len);
                if (!start_of_eol)
                        return (NULL);
                end_of_eol = start_of_eol + 1;
                break;
        default:
                return (NULL);
        }

        n_to_copy = start_of_eol - data;
        n_to_drain = end_of_eol - data;

        if ((line = malloc(n_to_copy+1)) == NULL) {
                event_warn("%s: out of memory", __func__);
                return (NULL);
        }

        memcpy(line, data, n_to_copy);
        line[n_to_copy] = '\0';

        evbuffer_drain(buffer, n_to_drain);
        if (n_read_out)
                *n_read_out = (size_t)n_to_copy;

        return (line);
}

/* Adds data to an event buffer */

static void
evbuffer_align(struct evbuffer *buf)
{
        memmove(buf->orig_buffer, buf->buffer, buf->off);
        buf->buffer = buf->orig_buffer;
        buf->misalign = 0;
}

/* Expands the available space in the event buffer to at least datlen */

int
evbuffer_expand(struct evbuffer *buf, size_t datlen)
{
        size_t used = buf->misalign + buf->off;

        assert(buf->totallen >= used);

        /* If we can fit all the data, then we don't have to do anything */
        if (buf->totallen - used >= datlen)
                return (0);
        /* If we would need to overflow to fit this much data, we can't
         * do anything. */
        if (datlen > SIZE_MAX - buf->off)
                return (-1);

        /*
         * If the misalignment fulfills our data needs, we just force an
         * alignment to happen.  Afterwards, we have enough space.
         */
        if (buf->totallen - buf->off >= datlen) {
                evbuffer_align(buf);
        } else {
                void *newbuf;
                size_t length = buf->totallen;
                size_t need = buf->off + datlen;

                if (length < 256)
                        length = 256;
                if (need < SIZE_MAX / 2) {
                        while (length < need) {
                                length <<= 1;
                        }
                } else {
                        length = need;
                }

                if (buf->orig_buffer != buf->buffer)
                        evbuffer_align(buf);
                if ((newbuf = recallocarray(buf->buffer, buf->totallen,
                    length, 1)) == NULL)
                        return (-1);

                buf->orig_buffer = buf->buffer = newbuf;
                buf->totallen = length;
        }

        return (0);
}

int
evbuffer_add(struct evbuffer *buf, const void *data, size_t datlen)
{
        size_t used = buf->misalign + buf->off;
        size_t oldoff = buf->off;

        if (buf->totallen - used < datlen) {
                if (evbuffer_expand(buf, datlen) == -1)
                        return (-1);
        }

        memcpy(buf->buffer + buf->off, data, datlen);
        buf->off += datlen;

        if (datlen && buf->cb != NULL)
                (*buf->cb)(buf, oldoff, buf->off, buf->cbarg);

        return (0);
}

void
evbuffer_drain(struct evbuffer *buf, size_t len)
{
        size_t oldoff = buf->off;

        if (len >= buf->off) {
                buf->off = 0;
                buf->buffer = buf->orig_buffer;
                buf->misalign = 0;
                goto done;
        }

        buf->buffer += len;
        buf->misalign += len;

        buf->off -= len;

 done:
        /* Tell someone about changes in this buffer */
        if (buf->off != oldoff && buf->cb != NULL)
                (*buf->cb)(buf, oldoff, buf->off, buf->cbarg);

}

/*
 * Reads data from a file descriptor into a buffer.
 */

#define EVBUFFER_MAX_READ       4096

int
evbuffer_read(struct evbuffer *buf, int fd, int howmuch)
{
        u_char *p;
        size_t oldoff = buf->off;
        int n = EVBUFFER_MAX_READ;

        if (ioctl(fd, FIONREAD, &n) == -1 || n <= 0) {
                n = EVBUFFER_MAX_READ;
        } else if (n > EVBUFFER_MAX_READ && n > howmuch) {
                /*
                 * It's possible that a lot of data is available for
                 * reading.  We do not want to exhaust resources
                 * before the reader has a chance to do something
                 * about it.  If the reader does not tell us how much
                 * data we should read, we artificially limit it.
                 */
                if ((size_t)n > buf->totallen << 2)
                        n = buf->totallen << 2;
                if (n < EVBUFFER_MAX_READ)
                        n = EVBUFFER_MAX_READ;
        }
        if (howmuch < 0 || howmuch > n)
                howmuch = n;

        /* If we don't have FIONREAD, we might waste some space here */
        if (evbuffer_expand(buf, howmuch) == -1)
                return (-1);

        /* We can append new data at this point */
        p = buf->buffer + buf->off;

        n = read(fd, p, howmuch);
        if (n == -1)
                return (-1);
        if (n == 0)
                return (0);

        buf->off += n;

        /* Tell someone about changes in this buffer */
        if (buf->off != oldoff && buf->cb != NULL)
                (*buf->cb)(buf, oldoff, buf->off, buf->cbarg);

        return (n);
}

int
evbuffer_write(struct evbuffer *buffer, int fd)
{
        int n;

        n = write(fd, buffer->buffer, buffer->off);
        if (n == -1)
                return (-1);
        if (n == 0)
                return (0);
        evbuffer_drain(buffer, n);

        return (n);
}

u_char *
evbuffer_find(struct evbuffer *buffer, const u_char *what, size_t len)
{
        u_char *search = buffer->buffer, *end = search + buffer->off;
        u_char *p;

        while (search < end &&
            (p = memchr(search, *what, end - search)) != NULL) {
                if (p + len > end)
                        break;
                if (memcmp(p, what, len) == 0)
                        return (p);
                search = p + 1;
        }

        return (NULL);
}

void evbuffer_setcb(struct evbuffer *buffer,
    void (*cb)(struct evbuffer *, size_t, size_t, void *),
    void *cbarg)
{
        buffer->cb = cb;
        buffer->cbarg = cbarg;
}