[multiple] optimize primitives, buffer_extend()

optimize buffer_* primitives

Other than buffer_string_set_length(), reallocate with one power-2 step
in size (or use the requested size, if larger).  This replaces the fixed
BUFFER_PIECE_SIZE round-up of only 64 bytes extension each reallocation,
which could lead to excessive reallocations in some scenarios.

buffer_extend() convenience routine to prep for batch append
(combines buffer_string_prepare_append() and buffer_commit())

mod_fastcgi, mod_scgi, mod_proxy and others now leverage buffer_extend()

mod_scgi directly performs little-endian encoding of short ints

http_response_write_header() optimizes writing response header,
leveraging buffer_extend()

modify mod_proxy to append line ends
similar to how it is done in http_response_write_header()
(removes one call to buffer_append_string_len())

1 files changed, 9 insertions, 2 deletions

diff --git a/src/buffer.h b/src/buffer.h
index d055c085..2a5bb4dc 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -62,6 +62,13 @@ char* buffer_string_prepare_copy(buffer *b, size_t size);
 __attribute_returns_nonnull__
 char* buffer_string_prepare_append(buffer *b, size_t size);
 
+/* extend and modify buffer for immediate addition of x bytes (differs from
+ * buffer_string_prepare_append() which only ensures space is available)
+ * returns pointer to which callers should immediately write x bytes
+ */
+__attribute_returns_nonnull__
+char* buffer_extend(buffer * const restrict b, size_t x);
+
 /* use after prepare_(copy,append) when you have written data to the buffer
  * to increase the buffer length by size. also sets the terminating zero.
  * requires enough space is present for the terminating zero (prepare with the
@@ -99,11 +106,11 @@ __attribute_cold__
 void buffer_free_ptr(buffer *b);
 
 void buffer_copy_string(buffer * restrict b, const char * restrict s);
-void buffer_copy_string_len(buffer * restrict b, const char * restrict s, size_t s_len);
+void buffer_copy_string_len(buffer * restrict b, const char * restrict s, size_t len);
 static inline void buffer_copy_buffer(buffer * restrict b, const buffer * restrict src);
 
 void buffer_append_string(buffer * restrict b, const char * restrict s);
-void buffer_append_string_len(buffer * restrict b, const char * restrict s, size_t s_len);
+void buffer_append_string_len(buffer * restrict b, const char * restrict s, size_t len);
 static inline void buffer_append_string_buffer(buffer * restrict b, const buffer * restrict src);
 
 #define buffer_append_uint_hex(b,len) buffer_append_uint_hex_lc((b),(len))