From 96944c8f6522afa9598456f1cb2dcae058e5a9f8 Mon Sep 17 00:00:00 2001
From: Jason Ekstrand <jason@jlekstrand.net>
Date: Mon, 4 Oct 2021 11:58:33 -0500
Subject: [PATCH] util/blob: Add align helpers

Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-by: Connor Abbott <cwabbott0@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13184>
---
 src/util/blob.c | 18 ++++++++++--------
 src/util/blob.h | 21 +++++++++++++++++++++
 2 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/src/util/blob.c b/src/util/blob.c
index db192146ac1..67f6bb2567c 100644
--- a/src/util/blob.c
+++ b/src/util/blob.c
@@ -82,9 +82,10 @@ grow_to_fit(struct blob *blob, size_t additional)
  *
  * \return True unless allocation fails
  */
-static bool
-align_blob(struct blob *blob, size_t alignment)
+bool
+blob_align(struct blob *blob, size_t alignment)
 {
+   assert(align64((uintptr_t)blob->data, alignment) == (uintptr_t)blob->data);
    const size_t new_size = align64(blob->size, alignment);
 
    if (blob->size < new_size) {
@@ -99,9 +100,10 @@ align_blob(struct blob *blob, size_t alignment)
    return true;
 }
 
-static void
-align_blob_reader(struct blob_reader *blob, size_t alignment)
+void
+blob_reader_align(struct blob_reader *blob, size_t alignment)
 {
+   assert(align64((uintptr_t)blob->data, alignment) == (uintptr_t)blob->data);
    blob->current = blob->data + align64(blob->current - blob->data, alignment);
 }
 
@@ -186,14 +188,14 @@ blob_reserve_bytes(struct blob *blob, size_t to_write)
 intptr_t
 blob_reserve_uint32(struct blob *blob)
 {
-   align_blob(blob, sizeof(uint32_t));
+   blob_align(blob, sizeof(uint32_t));
    return blob_reserve_bytes(blob, sizeof(uint32_t));
 }
 
 intptr_t
 blob_reserve_intptr(struct blob *blob)
 {
-   align_blob(blob, sizeof(intptr_t));
+   blob_align(blob, sizeof(intptr_t));
    return blob_reserve_bytes(blob, sizeof(intptr_t));
 }
 
@@ -201,7 +203,7 @@ blob_reserve_intptr(struct blob *blob)
 bool                                                     \
 name(struct blob *blob, type value)                      \
 {                                                        \
-   align_blob(blob, sizeof(value));                      \
+   blob_align(blob, sizeof(value));                      \
    return blob_write_bytes(blob, &value, sizeof(value)); \
 }
 
@@ -319,7 +321,7 @@ name(struct blob_reader *blob)             \
 {                                          \
    type ret;                               \
    int size = sizeof(ret);                 \
-   align_blob_reader(blob, size);          \
+   blob_reader_align(blob, size);          \
    if (! ensure_can_read(blob, size))      \
       return 0;                            \
    ret = *((type*) blob->current);         \
diff --git a/src/util/blob.h b/src/util/blob.h
index 051eaa01674..91b05901534 100644
--- a/src/util/blob.h
+++ b/src/util/blob.h
@@ -123,6 +123,16 @@ blob_finish(struct blob *blob)
 void
 blob_finish_get_buffer(struct blob *blob, void **buffer, size_t *size);
 
+/**
+ * Aligns the blob to the given alignment.
+ *
+ * \see blob_reader_align
+ *
+ * \return True unless allocation fails
+ */
+bool
+blob_align(struct blob *blob, size_t alignment);
+
 /**
  * Add some unstructured, fixed-size data to a blob.
  *
@@ -316,6 +326,17 @@ blob_write_string(struct blob *blob, const char *str);
 void
 blob_reader_init(struct blob_reader *blob, const void *data, size_t size);
 
+/**
+ * Align the current offset of the blob reader to the given alignment.
+ *
+ * This may be useful if you need the result of blob_read_bytes to have a
+ * particular alignment.  Note that this only aligns relative to blob->data
+ * and the alignment of the resulting pointer is only guaranteed if blob->data
+ * is also aligned to the requested alignment.
+ */
+void
+blob_reader_align(struct blob_reader *blob, size_t alignment);
+
 /**
  * Read some unstructured, fixed-size data from the current location, (and
  * update the current location to just past this data).