compiler/blob: Add a concept of a fixed-allocation blob

Reviewed-by: Nicolai Hähnle <[email protected]>
Reviewed-by: Jordan Justen <[email protected]>

2 files changed, 37 insertions, 1 deletions

diff --git a/src/compiler/blob.c b/src/compiler/blob.c
index 2e20a11dc0c..a78fcd41a76 100644
--- a/src/compiler/blob.c
+++ b/src/compiler/blob.c
@@ -52,6 +52,11 @@ grow_to_fit(struct blob *blob, size_t additional)
    if (blob->size + additional <= blob->allocated)
       return true;
 
+   if (blob->fixed_allocation) {
+      blob->out_of_memory = true;
+      return false;
+   }
+
    if (blob->allocated == 0)
       to_allocate = BLOB_INITIAL_SIZE;
    else
@@ -105,6 +110,17 @@ blob_init(struct blob *blob)
    blob->data = NULL;
    blob->allocated = 0;
    blob->size = 0;
+   blob->fixed_allocation = false;
+   blob->out_of_memory = false;
+}
+
+void
+blob_init_fixed(struct blob *blob, void *data, size_t size)
+{
+   blob->data = data;
+   blob->allocated = size;
+   blob->size = 0;
+   blob->fixed_allocation = true;
    blob->out_of_memory = false;
 }
 
diff --git a/src/compiler/blob.h b/src/compiler/blob.h
index 8a7a28b4f3c..e23e392eedd 100644
--- a/src/compiler/blob.h
+++ b/src/compiler/blob.h
@@ -56,6 +56,12 @@ struct blob {
    /** The number of bytes that have actual data written to them. */
    size_t size;
 
+   /** True if \c data a fixed allocation that we cannot resize
+    *
+    * \see blob_init_fixed
+    */
+   bool fixed_allocation;
+
    /**
     * True if we've ever failed to realloc or if we go pas the end of a fixed
     * allocation blob.
@@ -85,12 +91,26 @@ void
 blob_init(struct blob *blob);
 
 /**
+ * Init a new, fixed-size blob.
+ *
+ * A fixed-size blob has a fixed block of data that will not be freed on
+ * blob_finish and will never be grown.  If we hit the end, we simply start
+ * returning false from the write functions.
+ */
+void
+blob_init_fixed(struct blob *blob, void *data, size_t size);
+
+/**
  * Finish a blob and free its memory.
+ *
+ * If \blob was initialized with blob_init_fixed, the data pointer is
+ * considered to be owned by the user and will not be freed.
  */
 static inline void
 blob_finish(struct blob *blob)
 {
-   free(blob->data);
+   if (!blob->fixed_allocation)
+      free(blob->data);
 }
 
 /**