[Mesa-dev] [PATCH 1/7] ralloc: add a new printing helper ralloc_sprint_rewrite_tail

[Marek Olšák]

From: Marek Olšák <marek.olsak at amd.com>

This one is much faster when you don't need vsprintf.
---
 src/util/ralloc.c | 25 +++++++++++++++++++++++++
 src/util/ralloc.h | 24 ++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/src/util/ralloc.c b/src/util/ralloc.c
index 980e4e4..7976ca6 100644
--- a/src/util/ralloc.c
+++ b/src/util/ralloc.c
@@ -522,20 +522,45 @@ ralloc_vasprintf_rewrite_tail(char **str, size_t *start, const char *fmt,
    ptr = resize(*str, *start + new_length + 1);
    if (unlikely(ptr == NULL))
       return false;
 
    vsnprintf(ptr + *start, new_length + 1, fmt, args);
    *str = ptr;
    *start += new_length;
    return true;
 }
 
+bool
+ralloc_sprint_rewrite_tail(char **str, size_t *start, const char *text,
+                           unsigned text_length)
+{
+   char *ptr;
+
+   assert(str != NULL);
+
+   if (unlikely(*str == NULL)) {
+      /* Assuming a NULL context is probably bad, but it's expected behavior. */
+      *str = ralloc_strdup(NULL, text);
+      *start = strlen(*str);
+      return true;
+   }
+
+   ptr = resize(*str, *start + text_length + 1);
+   if (unlikely(ptr == NULL))
+      return false;
+
+   memcpy(ptr + *start, text, text_length + 1); /* also copy '\0' */
+   *str = ptr;
+   *start += text_length;
+   return true;
+}
+
 /***************************************************************************
  * Linear allocator for short-lived allocations.
  ***************************************************************************
  *
  * The allocator consists of a parent node (2K buffer), which requires
  * a ralloc parent, and child nodes (allocations). Child nodes can't be freed
  * directly, because the parent doesn't track them. You have to release
  * the parent node in order to release all its children.
  *
  * The allocator uses a fixed-sized buffer with a monotonically increasing
diff --git a/src/util/ralloc.h b/src/util/ralloc.h
index 3e2d342..6c31a6d 100644
--- a/src/util/ralloc.h
+++ b/src/util/ralloc.h
@@ -401,20 +401,44 @@ bool ralloc_asprintf_append (char **str, const char *fmt, ...)
  * \sa ralloc_strcat
  *
  * \p str will be updated to the new pointer unless allocation fails.
  *
  * \return True unless allocation failed.
  */
 bool ralloc_vasprintf_append(char **str, const char *fmt, va_list args);
 /// @}
 
 /**
+ * Rewrite the tail of an existing string, starting at a given index.
+ *
+ * Overwrites the contents of *str starting at \p start with "text",
+ * including a new null-terminator.  Allocates more memory as necessary.
+ *
+ * This can be used to append formatted text when the length of the existing
+ * string is already known, saving a strlen() call.
+ *
+ * \sa ralloc_asprintf_rewrite_tail
+ *
+ * \param str          The string to be updated.
+ * \param start        The index to start appending new data at.
+ * \param text         The input string terminated by zero.
+ * \param text_length  The length of the input string.
+ *
+ * \p str will be updated to the new pointer unless allocation fails.
+ * \p start will be increased by the length of the newly formatted text.
+ *
+ * \return True unless allocation failed.
+ */
+bool ralloc_sprint_rewrite_tail(char **str, size_t *start, const char *text,
+                                unsigned text_length);
+
+/**
  * Declare C++ new and delete operators which use ralloc.
  *
  * Placing this macro in the body of a class makes it possible to do:
  *
  * TYPE *var = new(mem_ctx) TYPE(...);
  * delete var;
  *
  * which is more idiomatic in C++ than calling ralloc.
  */
 #define DECLARE_ALLOC_CXX_OPERATORS_TEMPLATE(TYPE, ALLOC_FUNC)           \
-- 
2.7.4