src/lib/buffer.c

	buffer.c revision 02c335c23bf5fa225a467c19f2c063fb0dc7b8c3
/* Copyright (c) 2002-2016 Dovecot authors, see the included COPYING file */

/* @UNSAFE: whole file */

#include "lib.h"
#include "buffer.h"

struct real_buffer {
    /* public: */
    const unsigned char *r_buffer;
    size_t used;

    /* private: */
    unsigned char *w_buffer;
    size_t dirty, alloc;

    pool_t pool;

    unsigned int alloced:1;
    unsigned int dynamic:1;
};
typedef int buffer_check_sizes[COMPILE_ERROR_IF_TRUE(sizeof(struct real_buffer) > sizeof(buffer_t)) ?1:1];

static void buffer_alloc(struct real_buffer *buf, size_t size)
{
    i_assert(buf->w_buffer == NULL || buf->alloced);

    if (size == buf->alloc)
        return;

    i_assert(size > buf->alloc);

    buf->w_buffer = p_realloc(buf->pool, buf->w_buffer, buf->alloc, size);
    buf->alloc = size;

    buf->r_buffer = buf->w_buffer;
    buf->alloced = TRUE;
}

static inline void
buffer_check_limits(struct real_buffer *buf, size_t pos, size_t data_size)
{
    unsigned int extra;
    size_t new_size;

    if (unlikely((size_t)-1 - pos < data_size)) {
        i_panic("Buffer write out of range (%"PRIuSIZE_T
            " + %"PRIuSIZE_T")", pos, data_size);
    }
    new_size = pos + data_size;

    if (new_size > buf->used && buf->used < buf->dirty) {
        /* clear used..dirty area */
        size_t max = I_MIN(I_MIN(buf->alloc, buf->dirty), new_size);

        memset(buf->w_buffer + buf->used, 0, max - buf->used);
    }

    /* always keep +1 byte allocated available in case str_c() is called
       for this buffer. this is mainly for cases where the buffer is
       allocated from data stack, and str_c() is called in a separate stack
       frame. */
    extra = buf->dynamic ? 1 : 0;
    if (new_size + extra > buf->alloc) {
        if (unlikely(!buf->dynamic)) {
            i_panic("Buffer full (%"PRIuSIZE_T" > %"PRIuSIZE_T", "
                "pool %s)", pos + data_size, buf->alloc,
                buf->pool == NULL ? "<none>" :
                pool_get_name(buf->pool));
        }

        buffer_alloc(buf, pool_get_exp_grown_size(buf->pool, buf->alloc,
                              new_size + extra));
    }
#if 0
    else if (new_size > buf->used && buf->alloced &&
         !buf->pool->alloconly_pool && !buf->pool->datastack_pool) {
        void *new_buf;

        /* buffer's size increased: move the buffer's memory elsewhere.
           this should help catch bugs where old pointers are tried to
           be used to access the buffer's memory */
        new_buf = p_malloc(buf->pool, buf->alloc);
        memcpy(new_buf, buf->w_buffer, buf->alloc);
        p_free(buf->pool, buf->w_buffer);

        buf->w_buffer = new_buf;
        buf->r_buffer = new_buf;
    }
#endif

    if (new_size > buf->used)
        buf->used = new_size;
    i_assert(buf->used <= buf->alloc);
}

#undef buffer_create_from_data
void buffer_create_from_data(buffer_t *buffer, void *data, size_t size)
{
    struct real_buffer *buf;

    i_assert(sizeof(*buffer) >= sizeof(struct real_buffer));

    buf = (struct real_buffer *)buffer;
    memset(buf, 0, sizeof(*buf));
    buf->alloc = size;
    buf->r_buffer = buf->w_buffer = data;
    /* clear the whole memory area. unnecessary usually, but if the
       buffer is used by e.g. str_c() it tries to access uninitialized
       memory */
    memset(data, 0, size);
}

#undef buffer_create_from_const_data
void buffer_create_from_const_data(buffer_t *buffer,
                   const void *data, size_t size)
{
    struct real_buffer *buf;

    i_assert(sizeof(*buffer) >= sizeof(struct real_buffer));

    buf = (struct real_buffer *)buffer;
    memset(buf, 0, sizeof(*buf));

    buf->used = buf->alloc = size;
    buf->r_buffer = data;
    i_assert(buf->w_buffer == NULL);
}

buffer_t *buffer_create_dynamic(pool_t pool, size_t init_size)
{
    struct real_buffer *buf;

    buf = p_new(pool, struct real_buffer, 1);
    buf->pool = pool;
    buf->dynamic = TRUE;
    buffer_alloc(buf, init_size);
    return (buffer_t *)buf;
}

void buffer_free(buffer_t **_buf)
{
    struct real_buffer *buf = (struct real_buffer *)*_buf;

    *_buf = NULL;
    if (buf->alloced)
        p_free(buf->pool, buf->w_buffer);
    if (buf->pool != NULL)
        p_free(buf->pool, buf);
}

void *buffer_free_without_data(buffer_t **_buf)
{
    struct real_buffer *buf = (struct real_buffer *)*_buf;
    void *data;

    *_buf = NULL;

    data = buf->w_buffer;
    p_free(buf->pool, buf);
    return data;
}

pool_t buffer_get_pool(const buffer_t *_buf)
{
    const struct real_buffer *buf = (const struct real_buffer *)_buf;

    return buf->pool;
}

void buffer_reset(buffer_t *buf)
{
    buffer_set_used_size(buf, 0);
}

void buffer_write(buffer_t *_buf, size_t pos,
          const void *data, size_t data_size)
{
    struct real_buffer *buf = (struct real_buffer *)_buf;

    buffer_check_limits(buf, pos, data_size);
    memcpy(buf->w_buffer + pos, data, data_size);
}

void buffer_append(buffer_t *buf, const void *data, size_t data_size)
{
    buffer_write(buf, buf->used, data, data_size);
}

void buffer_append_c(buffer_t *buf, unsigned char chr)
{
    buffer_append(buf, &chr, 1);
}

void buffer_insert(buffer_t *_buf, size_t pos,
           const void *data, size_t data_size)
{
    struct real_buffer *buf = (struct real_buffer *)_buf;

    if (pos >= buf->used)
        buffer_write(_buf, pos, data, data_size);
    else {
        buffer_copy(_buf, pos + data_size, _buf, pos, (size_t)-1);
        memcpy(buf->w_buffer + pos, data, data_size);
    }
}

void buffer_delete(buffer_t *_buf, size_t pos, size_t size)
{
    struct real_buffer *buf = (struct real_buffer *)_buf;
    size_t end_size;

    if (pos >= buf->used)
        return;
    end_size = buf->used - pos;

    if (size < end_size) {
        /* delete from between */
        end_size -= size;
        memmove(buf->w_buffer + pos,
            buf->w_buffer + pos + size, end_size);
    } else {
        /* delete the rest of the buffer */
        end_size = 0;
    }

    buffer_set_used_size(_buf, pos + end_size);
}

void buffer_write_zero(buffer_t *_buf, size_t pos, size_t data_size)
{
    struct real_buffer *buf = (struct real_buffer *)_buf;

    buffer_check_limits(buf, pos, data_size);
    memset(buf->w_buffer + pos, 0, data_size);
}

void buffer_append_zero(buffer_t *buf, size_t data_size)
{
    buffer_write_zero(buf, buf->used, data_size);
}

void buffer_insert_zero(buffer_t *_buf, size_t pos, size_t data_size)
{
    struct real_buffer *buf = (struct real_buffer *)_buf;

    if (pos >= buf->used)
        buffer_write_zero(_buf, pos, data_size);
    else {
        buffer_copy(_buf, pos + data_size, _buf, pos, (size_t)-1);
        memset(buf->w_buffer + pos, 0, data_size);
    }
}

void buffer_copy(buffer_t *_dest, size_t dest_pos,
         const buffer_t *_src, size_t src_pos, size_t copy_size)
{
    struct real_buffer *dest = (struct real_buffer *)_dest;
    const struct real_buffer *src = (const struct real_buffer *)_src;
    size_t max_size;

    i_assert(src_pos <= src->used);

    max_size = src->used - src_pos;
    if (copy_size > max_size)
        copy_size = max_size;

    buffer_check_limits(dest, dest_pos, copy_size);
    if (src == dest) {
        memmove(dest->w_buffer + dest_pos,
            src->r_buffer + src_pos, copy_size);
    } else {
        memcpy(dest->w_buffer + dest_pos,
               src->r_buffer + src_pos, copy_size);
    }
}

void buffer_append_buf(buffer_t *dest, const buffer_t *src,
               size_t src_pos, size_t copy_size)
{
    buffer_copy(dest, dest->used, src, src_pos, copy_size);
}

void *buffer_get_space_unsafe(buffer_t *_buf, size_t pos, size_t size)
{
    struct real_buffer *buf = (struct real_buffer *)_buf;

    buffer_check_limits(buf, pos, size);
    return buf->w_buffer + pos;
}

void *buffer_append_space_unsafe(buffer_t *buf, size_t size)
{
    return buffer_get_space_unsafe(buf, buf->used, size);
}

void *buffer_get_modifiable_data(const buffer_t *_buf, size_t *used_size_r)
{
    const struct real_buffer *buf = (const struct real_buffer *)_buf;

    if (used_size_r != NULL)
        *used_size_r = buf->used;
    return buf->w_buffer;
}

void buffer_set_used_size(buffer_t *_buf, size_t used_size)
{
    struct real_buffer *buf = (struct real_buffer *)_buf;

    i_assert(used_size <= buf->alloc);

    if (buf->used > buf->dirty)
        buf->dirty = buf->used;

    buf->used = used_size;
}

size_t buffer_get_size(const buffer_t *_buf)
{
    const struct real_buffer *buf = (const struct real_buffer *)_buf;

    return buf->alloc;
}

size_t buffer_get_writable_size(const buffer_t *_buf)
{
    const struct real_buffer *buf = (const struct real_buffer *)_buf;

    if (!buf->dynamic || buf->alloc == 0)
        return buf->alloc;

    /* we reserve +1 for str_c() NUL in buffer_check_limits(), so don't
       include that in our return value. otherwise the caller might
       increase the buffer's alloc size unnecessarily when it just wants
       to access the entire buffer. */
    return buf->alloc-1;
}

bool buffer_cmp(const buffer_t *buf1, const buffer_t *buf2)
{
    if (buf1->used != buf2->used)
        return FALSE;

    return memcmp(buf1->data, buf2->data, buf1->used) == 0;
}

void buffer_verify_pool(buffer_t *_buf)
{
    const struct real_buffer *buf = (const struct real_buffer *)_buf;
    void *ret;

    if (buf->pool != NULL && buf->pool->datastack_pool && buf->alloc > 0) {
        /* this doesn't really do anything except verify the
           stack frame */
        ret = p_realloc(buf->pool, buf->w_buffer,
                buf->alloc, buf->alloc);
        i_assert(ret == buf->w_buffer);
    }
}