[Mesa-dev] [PATCH 04/12] glcpp: Use string_buffer for continuations removal

[Vladislav Egorov]

Migrate removal of line continuations to string_buffer. Before this
it used ralloc_strncat() to append strings, which internally
each time calculates strlen() of its argument. Its argument is
entire shader, so it multiple time scans the whole shader text.
---
 src/compiler/glsl/glcpp/glcpp.h | 11 +++++++++--
 src/compiler/glsl/glcpp/pp.c    | 28 +++++++++++++++++++++-------
 2 files changed, 30 insertions(+), 9 deletions(-)

diff --git a/src/compiler/glsl/glcpp/glcpp.h b/src/compiler/glsl/glcpp/glcpp.h
index a9c08e6..34f8b66 100644
--- a/src/compiler/glsl/glcpp/glcpp.h
+++ b/src/compiler/glsl/glcpp/glcpp.h
@@ -275,9 +275,9 @@ glcpp_printf(glcpp_parser_t *parser, struct string_buffer 
*str,
 
 /* Inlining is necessary to resolve length of literal strings statically */
 static inline bool
-glcpp_append(glcpp_parser_t *parser, struct string_buffer *str, const char *s)
+glcpp_append_length(glcpp_parser_t *parser, struct string_buffer *str,
+                   const char *s, size_t len)
 {
-       size_t len = strlen(s);
        if (likely(glcpp_strbuffer_ensure_capacity(parser, str, len))) {
                /* Don't copy null-terminator, str->buf is
                 * not a null-terminating string
@@ -291,6 +291,13 @@ glcpp_append(glcpp_parser_t *parser, struct string_buffer 
*str, const char *s)
 }
 
 static inline bool
+glcpp_append(glcpp_parser_t *parser, struct string_buffer *str, const char *s)
+{
+       size_t len = strlen(s);
+       return glcpp_append_length(parser, str, s, len);
+}
+
+static inline bool
 glcpp_append_char(glcpp_parser_t *parser, struct string_buffer *str, char ch)
 {
        assert(str->capacity > 0 && ch != '\0');
diff --git a/src/compiler/glsl/glcpp/pp.c b/src/compiler/glsl/glcpp/pp.c
index 7fbadf9..af4ec93 100644
--- a/src/compiler/glsl/glcpp/pp.c
+++ b/src/compiler/glsl/glcpp/pp.c
@@ -229,11 +229,16 @@ skip_newline (const char *str)
 static char *
 remove_line_continuations(glcpp_parser_t *ctx, const char *shader)
 {
-       char *clean = ralloc_strdup(ctx, "");
+       struct string_buffer sb;
        const char *backslash, *newline, *search_start;
         const char *cr, *lf;
         char newline_separator[3];
        int collapsed_newlines = 0;
+       int separator_len;
+
+       sb.capacity = 4096 - RALLOC_OVERHEAD;
+       sb.buf = ralloc_size(ctx, sb.capacity);
+       sb.length = 0;
 
        search_start = shader;
 
@@ -273,6 +278,7 @@ remove_line_continuations(glcpp_parser_t *ctx, const char 
*shader)
                newline_separator[0] = '\n';
                newline_separator[1] = '\r';
        }
+       separator_len = strlen(newline_separator);
 
        while (true) {
                backslash = strchr(search_start, '\\');
@@ -294,10 +300,12 @@ remove_line_continuations(glcpp_parser_t *ctx, const char 
*shader)
                        if (newline &&
                            (backslash == NULL || newline < backslash))
                        {
-                               ralloc_strncat(&clean, shader,
-                                              newline - shader + 1);
+                               glcpp_append_length(ctx, &sb, shader,
+                                                   newline - shader + 1);
                                while (collapsed_newlines) {
-                                       ralloc_strcat(&clean, 
newline_separator);
+                                       glcpp_append_length(ctx, &sb,
+                                                           newline_separator,
+                                                           separator_len);
                                        collapsed_newlines--;
                                }
                                shader = skip_newline (newline);
@@ -318,15 +326,21 @@ remove_line_continuations(glcpp_parser_t *ctx, const char 
*shader)
                if (backslash[1] == '\r' || backslash[1] == '\n')
                {
                        collapsed_newlines++;
-                       ralloc_strncat(&clean, shader, backslash - shader);
+                       glcpp_append_length(ctx, &sb, shader,
+                                           backslash - shader);
                        shader = skip_newline (backslash + 1);
                        search_start = shader;
                }
        }
 
-       ralloc_strcat(&clean, shader);
+       glcpp_append(ctx, &sb, shader);
+
+       /* string_buffer's string is not null-terminated, but it has enough
+        * of space for '\0'. Don't forget to put null-terminator.
+        */
+       sb.buf[sb.length] = '\0';
 
-       return clean;
+       return sb.buf;
 }
 
 int
-- 
2.7.4

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