* Gonglei (Arei) (address@hidden) wrote:
<snip>
+/**
+ * Grow the QEMUSizedBuffer to the given size and allocated
+ * memory for it.
+ *
+ * @qsb: A QEMUSizedBuffer
+ * @new_size: The new size of the buffer
+ *
+ * Returns an error code in case of memory allocation failure
+ * or the new size of the buffer otherwise. The returned size
+ * may be greater or equal to @new_size.
+ */
+static ssize_t qsb_grow(QEMUSizedBuffer *qsb, size_t new_size)
+{
+ size_t needed_chunks, i;
+ size_t chunk_size = QSB_CHUNK_SIZE;
+
+ if (qsb->size < new_size) {
+ needed_chunks = DIV_ROUND_UP(new_size - qsb->size,
+ chunk_size);
+
+ qsb->iov = g_realloc_n(qsb->iov, qsb->n_iov + needed_chunks,
+ sizeof(struct iovec));
+ if (qsb->iov == NULL) {
+ return -ENOMEM;
+ }
OK...
Is it? https://developer.gnome.org/glib/stable/glib-Memory-Allocation.html
says that g_realloc_n is 'similar to g_realloc()' except for overflow
protection,
g_realloc() doesn't say what it's behaviour on OOM is, but g_try_realloc says
that 'Contrast with g_realloc(), which aborts the program on failure'
So the only case iov will return NULL there is if the size is 0 which it can't
be. So should that be a g_try_realloc_n ?
+
+ for (i = qsb->n_iov; i < qsb->n_iov + needed_chunks; i++) {
+ qsb->iov[i].iov_base = g_malloc0(chunk_size);
+ qsb->iov[i].iov_len = chunk_size;
+ }
+
+ qsb->n_iov += needed_chunks;
+ qsb->size += (needed_chunks * chunk_size);
+ }
+
+ return qsb->size;
+}
+
+/**
+ * Write into the QEMUSizedBuffer at a given position and a given
+ * number of bytes. This function will automatically grow the
+ * QEMUSizedBuffer.
+ *
+ * @qsb: A QEMUSizedBuffer
+ * @source: A byte array to copy data from
+ * @pos: The position withing the @qsb to write data to
+ * @size: The number of bytes to copy into the @qsb
+ *
+ * Returns an error code in case of memory allocation failure,
+ * @size otherwise.
+ */
+ssize_t qsb_write_at(QEMUSizedBuffer *qsb, const uint8_t *source,
+ off_t pos, size_t count)
+{
+ ssize_t rc = qsb_grow(qsb, pos + count);
+ size_t to_copy;
+ size_t all_copy = count;
+ const struct iovec *iov;
+ ssize_t index;
+ char *dest;
+ off_t d_off, s_off = 0;
+
+ if (rc < 0) {
+ return rc;
+ }
+
OK...
+ if (pos + count > qsb->used) {
+ qsb->used = pos + count;
+ }
+
+ index = qsb_get_iovec(qsb, pos, &d_off);
+ if (index < 0) {
+ return 0;
+ }
+
+ while (all_copy > 0) {
+ iov = &qsb->iov[index];
+
+ dest = iov->iov_base;
+
+ to_copy = iov->iov_len - d_off;
+ if (to_copy > all_copy) {
+ to_copy = all_copy;
+ }
+
+ memcpy(&dest[d_off], &source[s_off], to_copy);
+
+ s_off += to_copy;
+ all_copy -= to_copy;
+
+ d_off = 0;
+ index++;
+ }
+
+ return count;
+}
+
+/**
+ * Create an exact copy of the given QEMUSizedBuffer.
+ *
+ * @qsb : A QEMUSizedBuffer
+ *
+ * Returns a clone of @qsb
+ */
+QEMUSizedBuffer *qsb_clone(const QEMUSizedBuffer *qsb)
+{
+ QEMUSizedBuffer *out = qsb_create(NULL, qsb_get_length(qsb));
+ size_t i;
+ off_t pos = 0;
+
+ for (i = 0; i < qsb->n_iov; i++) {
+ pos += qsb_write_at(out, qsb->iov[i].iov_base,
+ pos, qsb->iov[i].iov_len);
If qsb_write_at() return -ENOMEM, just simply add it to pos ?
qsb_create uses g_new0 so it will abort on out of memory;
what should qsb_clone do if qsb_write_at returns -ENOMEM?
(Admittedly anything is better than getting the position wrong).
I guess the choice is to allow it to return NULL, tidying up
and offering the chance sometime in the future of tidying up
the other allocators.