glsl: Add blob.c---a simple interface for serializing data

This new interface allows for writing a series of objects to a chunk
of memory (a "blob").. The allocated memory is maintained within the
blob itself, (and re-allocated by doubling when necessary).

There are also functions for reading objects from a blob as well. If
code attempts to read beyond the available memory, the read functions
return 0 values (or its moral equivalent) without reading past the
allocated memory. Once the caller is done with the reads, it can check
blob->overrun to ensure whether any invalid values were previously
returned due to attempts to read too far.

Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>

1 files changed, 300 insertions, 0 deletions

diff --git a/src/glsl/blob.c b/src/glsl/blob.c
new file mode 100644
index 0000000..a4003cf
--- /dev/null
+++ b/src/glsl/blob.c
@@ -0,0 +1,300 @@
+/*
+ * Copyright © 2014 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#include <string.h>
+
+#include "main/macros.h"
+#include "util/ralloc.h"
+#include "blob.h"
+
+#define BLOB_INITIAL_SIZE 4096
+
+/* Ensure that \blob will be able to fit an additional object of size
+ * \additional.  The growing (if any) will occur by doubling the existing
+ * allocation.
+ */
+static bool
+grow_to_fit(struct blob *blob, size_t additional)
+{
+   size_t to_allocate;
+   uint8_t *new_data;
+
+   if (blob->size + additional <= blob->allocated)
+      return true;
+
+   if (blob->allocated == 0)
+      to_allocate = BLOB_INITIAL_SIZE;
+   else
+      to_allocate = blob->allocated * 2;
+
+   to_allocate = MAX2(to_allocate, blob->allocated + additional);
+
+   new_data = reralloc_size(blob, blob->data, to_allocate);
+   if (new_data == NULL)
+      return false;
+
+   blob->data = new_data;
+   blob->allocated = to_allocate;
+
+   return true;
+}
+
+/* Align the blob->size so that reading or writing a value at (blob->data +
+ * blob->size) will result in an access aligned to a granularity of \alignment
+ * bytes.
+ *
+ * \return True unless allocation fails
+ */
+static bool
+align_blob(struct blob *blob, size_t alignment)
+{
+   const size_t new_size = ALIGN(blob->size, alignment);
+
+   if (! grow_to_fit (blob, new_size - blob->size))
+      return false;
+
+   blob->size = new_size;
+
+   return true;
+}
+
+static void
+align_blob_reader(struct blob_reader *blob, size_t alignment)
+{
+   blob->current = blob->data + ALIGN(blob->current - blob->data, alignment);
+}
+
+struct blob *
+blob_create(void *mem_ctx)
+{
+   struct blob *blob;
+
+   blob = ralloc(mem_ctx, struct blob);
+   if (blob == NULL)
+      return NULL;
+
+   blob->data = NULL;
+   blob->allocated = 0;
+   blob->size = 0;
+
+   return blob;
+}
+
+bool
+blob_write_bytes(struct blob *blob, const void *bytes, size_t to_write)
+{
+   if (! grow_to_fit(blob, to_write))
+       return false;
+
+   memcpy(blob->data + blob->size, bytes, to_write);
+   blob->size += to_write;
+
+   return true;
+}
+
+uint8_t *
+blob_reserve_bytes(struct blob *blob, size_t to_write)
+{
+   uint8_t *ret;
+
+   if (! grow_to_fit (blob, to_write))
+      return NULL;
+
+   ret = blob->data + blob->size;
+   blob->size += to_write;
+
+   return ret;
+}
+
+bool
+blob_write_uint32(struct blob *blob, uint32_t value)
+{
+   align_blob(blob, sizeof(value));
+
+   return blob_write_bytes(blob, &value, sizeof(value));
+}
+
+bool
+blob_write_uint64(struct blob *blob, uint64_t value)
+{
+   align_blob(blob, sizeof(value));
+
+   return blob_write_bytes(blob, &value, sizeof(value));
+}
+
+bool
+blob_write_intptr(struct blob *blob, intptr_t value)
+{
+   align_blob(blob, sizeof(value));
+
+   return blob_write_bytes(blob, &value, sizeof(value));
+}
+
+bool
+blob_write_string(struct blob *blob, const char *str)
+{
+   return blob_write_bytes(blob, str, strlen(str) + 1);
+}
+
+void
+blob_reader_init(struct blob_reader *blob, uint8_t *data, size_t size)
+{
+   blob->data = data;
+   blob->end = data + size;
+   blob->current = data;
+   blob->overrun = false;
+}
+
+/* Check that an object of size \size can be read from this blob.
+ *
+ * If not, set blob->overrun to indicate that we attempted to read too far.
+ */
+static bool
+ensure_can_read(struct blob_reader *blob, size_t size)
+{
+   if (blob->current < blob->end && blob->end - blob->current >= size)
+      return true;
+
+   blob->overrun = true;
+
+   return false;
+}
+
+void *
+blob_read_bytes(struct blob_reader *blob, size_t size)
+{
+   void *ret;
+
+   if (! ensure_can_read (blob, size))
+      return NULL;
+
+   ret = blob->current;
+
+   blob->current += size;
+
+   return ret;
+}
+
+void
+blob_copy_bytes(struct blob_reader *blob, uint8_t *dest, size_t size)
+{
+   uint8_t *bytes;
+
+   bytes = blob_read_bytes(blob, size);
+   if (bytes == NULL)
+      return;
+
+   memcpy(dest, bytes, size);
+}
+
+/* These next three read functions have identical form. If we add any beyond
+ * these first three we should probably switch to generating these with a
+ * preprocessor macro.
+*/
+uint32_t
+blob_read_uint32(struct blob_reader *blob)
+{
+   uint32_t ret;
+   int size = sizeof(ret);
+
+   align_blob_reader(blob, size);
+
+   if (! ensure_can_read(blob, size))
+      return 0;
+
+   ret = *((uint32_t*) blob->current);
+
+   blob->current += size;
+
+   return ret;
+}
+
+uint64_t
+blob_read_uint64(struct blob_reader *blob)
+{
+   uint64_t ret;
+   int size = sizeof(ret);
+
+   align_blob_reader(blob, size);
+
+   if (! ensure_can_read(blob, size))
+      return 0;
+
+   ret = *((uint64_t*) blob->current);
+
+   blob->current += size;
+
+   return ret;
+}
+
+intptr_t
+blob_read_intptr(struct blob_reader *blob)
+{
+   intptr_t ret;
+   int size = sizeof(ret);
+
+   align_blob_reader(blob, size);
+
+   if (! ensure_can_read(blob, size))
+      return 0;
+
+   ret = *((intptr_t *) blob->current);
+
+   blob->current += size;
+
+   return ret;
+}
+
+char *
+blob_read_string(struct blob_reader *blob)
+{
+   int size;
+   char *ret;
+   uint8_t *nul;
+
+   /* If we're already at the end, then this is an overrun. */
+   if (blob->current >= blob->end) {
+      blob->overrun = true;
+      return NULL;
+   }
+
+   /* Similarly, if there is no zero byte in the data remaining in this blob,
+    * we also consider that an overrun.
+    */
+   nul = memchr(blob->current, 0, blob->end - blob->current);
+
+   if (nul == NULL) {
+      blob->overrun = true;
+      return NULL;
+   }
+
+   size = nul - blob->current + 1;
+
+   assert(ensure_can_read(blob, size));
+
+   ret = (char *) blob->current;
+
+   blob->current += size;
+
+   return ret;
+}