From 668df28967b8abd2893383e4d20b16cfe99dfdeb Mon Sep 17 00:00:00 2001
From: guysv <sviryguy@gmail.com>
Date: Sun, 8 Mar 2020 18:40:07 +0200
Subject: [PATCH] Add support for precomputed compression

If a client indicates that it supports gzip, then look for a `.gz`
variation of requested file. If such gzipped file exists, send it
instead and set the appropriate headers.

Range requests and dirlist requests are not supported.
---
 http.c | 24 ++++++++++++++++++++++--
 http.h |  1 +
 resp.c |  5 +++--
 resp.h |  2 +-
 4 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/http.c b/http.c
index efc4136..a654514 100644
--- a/http.c
+++ b/http.c
@@ -25,6 +25,7 @@ const char *req_field_str[] = {
 	[REQ_HOST]    = "Host",
 	[REQ_RANGE]   = "Range",
 	[REQ_MOD]     = "If-Modified-Since",
+	[REQ_ENCODE]  = "Accept-Encoding",
 };
 
 const char *req_method_str[] = {
@@ -349,7 +350,7 @@ enum status
 http_send_response(int fd, struct request *r)
 {
 	struct in6_addr res;
-	struct stat st;
+	struct stat st, gzst;
 	struct tm tm;
 	size_t len, i;
 	off_t lower, upper;
@@ -604,5 +605,24 @@ http_send_response(int fd, struct request *r)
 		}
 	}
 
-	return resp_file(fd, RELPATH(realtarget), r, &st, mime, lower, upper);
+	/* encoding-compression */
+	if (r->field[REQ_ENCODE][0] && !r->field[REQ_RANGE][0]) {
+		for (p = r->field[REQ_ENCODE]; p; p = strchr(p, ','), p ? p++ : p) {
+			/* skip whitespace */
+			for (; *p == ' ' || *p == '\t'; p++)
+			;
+			if (!strncasecmp(p, "gzip", sizeof("gzip")-1) &&
+					!esnprintf(tmptarget, sizeof(tmptarget), "%s%s", realtarget,
+							".gz") &&
+					!stat(RELPATH(tmptarget), &gzst) &&
+					S_ISREG(gzst.st_mode)) {
+				lower = 0;
+				upper = gzst.st_size-1;
+				return resp_file(fd, RELPATH(tmptarget), r, &gzst, mime,
+								"Content-Encoding: gzip\r\n", lower, upper);
+			}
+		}
+	}
+
+	return resp_file(fd, RELPATH(realtarget), r, &st, mime, "", lower, upper);
 }
diff --git a/http.h b/http.h
index cd1ba22..26ced90 100644
--- a/http.h
+++ b/http.h
@@ -11,6 +11,7 @@ enum req_field {
 	REQ_HOST,
 	REQ_RANGE,
 	REQ_MOD,
+	REQ_ENCODE,
 	NUM_REQ_FIELDS,
 };
 
diff --git a/resp.c b/resp.c
index 3075c28..bf35ac8 100644
--- a/resp.c
+++ b/resp.c
@@ -111,7 +111,7 @@ cleanup:
 
 enum status
 resp_file(int fd, char *name, struct request *r, struct stat *st, char *mime,
-          off_t lower, off_t upper)
+          char *encoding, off_t lower, off_t upper)
 {
 	FILE *fp;
 	enum status s;
@@ -142,10 +142,11 @@ resp_file(int fd, char *name, struct request *r, struct stat *st, char *mime,
 	            "Connection: close\r\n"
 	            "Last-Modified: %s\r\n"
 	            "Content-Type: %s\r\n"
+				"%s"
 	            "Content-Length: %zu\r\n",
 	            s, status_str[s], timestamp(time(NULL), t1),
 	            timestamp(st->st_mtim.tv_sec, t2), mime,
-	            upper - lower + 1) < 0) {
+	            encoding, upper - lower + 1) < 0) {
 		s = S_REQUEST_TIMEOUT;
 		goto cleanup;
 	}
diff --git a/resp.h b/resp.h
index d5928ef..ccfaaad 100644
--- a/resp.h
+++ b/resp.h
@@ -9,6 +9,6 @@
 
 enum status resp_dir(int, char *, struct request *);
 enum status resp_file(int, char *, struct request *, struct stat *, char *,
-                      off_t, off_t);
+                      char *, off_t, off_t);
 
 #endif /* RESP_H */
-- 
2.25.1