httpd: optional support for gzip-compressed pages

function                                             old     new   delta
send_file_and_exit                                   662     761     +99
handle_incoming_and_exit                            2756    2830     +74
send_headers                                         603     654     +51
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 224/0)             Total: 224 bytes

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

2 files changed, 60 insertions, 4 deletions

diff --git a/networking/Config.src b/networking/Config.src
index 2d29c423a..8604c53e9 100644
--- a/networking/Config.src
+++ b/networking/Config.src
@@ -270,6 +270,14 @@ config FEATURE_HTTPD_PROXY
           Then a request to /url/myfile will be forwarded to
           http://hostname[:port]/new/path/myfile.
 
+config FEATURE_HTTPD_GZIP
+        bool "Support for GZIP content encoding"
+        default y
+        depends on HTTPD
+        help
+          Makes httpd send files using GZIP content encoding if the
+          client supports it and a pre-compressed <file>.gz exists.
+
 config IFCONFIG
         bool "ifconfig"
         default y
diff --git a/networking/httpd.c b/networking/httpd.c
index 12bad597a..cad45cd5d 100644
--- a/networking/httpd.c
+++ b/networking/httpd.c
@@ -277,6 +277,10 @@ struct globals {
 #if ENABLE_FEATURE_HTTPD_PROXY
         Htaccess_Proxy *proxy;
 #endif
+#if ENABLE_FEATURE_HTTPD_GZIP
+        /* client can handle gzip / we are going to send gzip */
+        smallint content_gzip;
+#endif
 };
 #define G (*ptr_to_globals)
 #define verbose           (G.verbose          )
@@ -319,6 +323,11 @@ enum {
 #define hdr_cnt           (G.hdr_cnt          )
 #define http_error_page   (G.http_error_page  )
 #define proxy             (G.proxy            )
+#if ENABLE_FEATURE_HTTPD_GZIP
+# define content_gzip     (G.content_gzip     )
+#else
+# define content_gzip     0
+#endif
 #define INIT_G() do { \
         SET_PTR_TO_GLOBALS(xzalloc(sizeof(G))); \
         IF_FEATURE_HTTPD_BASIC_AUTH(g_realm = "Web Server Authentication";) \
@@ -1027,10 +1036,14 @@ static void send_headers(int responseNum)
 #endif
                         "Last-Modified: %s\r\n%s %"OFF_FMT"u\r\n",
                                 tmp_str,
-                                "Content-length:",
+                                content_gzip ? "Transfer-length:" : "Content-length:",
                                 file_size
                 );
         }
+
+        if (content_gzip)
+                len += sprintf(iobuf + len, "Content-Encoding: gzip\r\n");
+
         iobuf[len++] = '\r';
         iobuf[len++] = '\n';
         if (infoString) {
@@ -1500,7 +1513,22 @@ static NOINLINE void send_file_and_exit(const char *url, int what)
         int fd;
         ssize_t count;
 
-        fd = open(url, O_RDONLY);
+        if (content_gzip) {
+                /* does <url>.gz exist? Then use it instead */
+                char *gzurl = xasprintf("%s.gz", url);
+                fd = open(gzurl, O_RDONLY);
+                free(gzurl);
+                if (fd != -1) {
+                        struct stat sb;
+                        fstat(fd, &sb);
+                        file_size = sb.st_size;
+                } else {
+                        IF_FEATURE_HTTPD_GZIP(content_gzip = 0;)
+                        fd = open(url, O_RDONLY);
+                }
+        } else {
+                fd = open(url, O_RDONLY);
+        }
         if (fd < 0) {
                 if (DEBUG)
                         bb_perror_msg("can't open '%s'", url);
@@ -1583,8 +1611,11 @@ static NOINLINE void send_file_and_exit(const char *url, int what)
                         url, found_mime_type);
 
 #if ENABLE_FEATURE_HTTPD_RANGES
-        if (what == SEND_BODY)
-                range_start = 0; /* err pages and ranges don't mix */
+        if (what == SEND_BODY /* err pages and ranges don't mix */
+         || content_gzip /* we are sending compressed page: can't do ranges */  ///why?
+        ) {
+                range_start = 0;
+        }
         range_len = MAXINT(off_t);
         if (range_start) {
                 if (!range_end) {
@@ -2048,6 +2079,23 @@ static void handle_incoming_and_exit(const len_and_sockaddr *fromAddr)
                                 }
                         }
 #endif
+#if ENABLE_FEATURE_HTTPD_GZIP
+                        if (STRNCASECMP(iobuf, "Accept-Encoding:") == 0) {
+                                char *s = iobuf + sizeof("Accept-Encoding:")-1;
+                                while (*s) {
+                                        ///is "Accept-Encoding: compress,gzip" valid?
+                                        // (that is, no space after ',') -
+                                        // this code won't handle that
+                                        s = skip_whitespace(s);
+                                        if (STRNCASECMP(s, "gzip") == 0)
+                                                content_gzip = 1;
+                                        /* Note: we do not support "gzip;q=0"
+                                         * method of _disabling_ gzip
+                                         * delivery */
+                                        s = skip_non_whitespace(s);
+                                }
+                        }
+#endif
                 } /* while extra header reading */
         }