From fd65b0fbbdb405425a14d0e49f5366667550b1c2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Olivier=20Mengu=C3=A9?= <dolmen@cpan.org>
Date: Tue, 13 Oct 2015 00:52:08 +0200
Subject: [PATCH] src: refactor method parsing

Use a switch and a macro to branch parsing of HTTP methods.
Easier to read and much shorter.

In this commit, the order of branches dispatching is the same as in the
original code, to ease review. Reordering branches by descending
frequency will improve speed too.

PR-URL: https://github.com/nodejs/http-parser/pull/273
Reviewed-By: Fedor Indutny <fedor@indutny.com>
---
 http_parser.c | 111 ++++++++++++++------------------------------------
 1 file changed, 31 insertions(+), 80 deletions(-)

diff --git a/http_parser.c b/http_parser.c
index 98e0b9f..d0c77ea 100644
--- a/http_parser.c
+++ b/http_parser.c
@@ -1007,89 +1007,40 @@ reexecute:
           UPDATE_STATE(s_req_spaces_before_url);
         } else if (ch == matcher[parser->index]) {
           ; /* nada */
-        } else if (parser->method == HTTP_CONNECT) {
-          if (parser->index == 1 && ch == 'H') {
-            parser->method = HTTP_CHECKOUT;
-          } else if (parser->index == 2  && ch == 'P') {
-            parser->method = HTTP_COPY;
-          } else {
-            SET_ERRNO(HPE_INVALID_METHOD);
-            goto error;
-          }
-        } else if (parser->method == HTTP_MKCOL) {
-          if (parser->index == 1 && ch == 'O') {
-            parser->method = HTTP_MOVE;
-          } else if (parser->index == 1 && ch == 'E') {
-            parser->method = HTTP_MERGE;
-          } else if (parser->index == 1 && ch == '-') {
-            parser->method = HTTP_MSEARCH;
-          } else if (parser->index == 2 && ch == 'A') {
-            parser->method = HTTP_MKACTIVITY;
-          } else if (parser->index == 3 && ch == 'A') {
-            parser->method = HTTP_MKCALENDAR;
-          } else {
-            SET_ERRNO(HPE_INVALID_METHOD);
-            goto error;
-          }
-        } else if (parser->method == HTTP_SUBSCRIBE) {
-          if (parser->index == 1 && ch == 'E') {
-            parser->method = HTTP_SEARCH;
-          } else {
-            SET_ERRNO(HPE_INVALID_METHOD);
-            goto error;
-          }
-        } else if (parser->method == HTTP_REPORT) {
-            if (parser->index == 2 && ch == 'B') {
-              parser->method = HTTP_REBIND;
-            } else {
-              SET_ERRNO(HPE_INVALID_METHOD);
-              goto error;
-            }
-        } else if (parser->index == 1) {
-          if (parser->method == HTTP_POST) {
-            if (ch == 'R') {
-              parser->method = HTTP_PROPFIND; /* or HTTP_PROPPATCH */
-            } else if (ch == 'U') {
-              parser->method = HTTP_PUT; /* or HTTP_PURGE */
-            } else if (ch == 'A') {
-              parser->method = HTTP_PATCH;
-            } else {
-              SET_ERRNO(HPE_INVALID_METHOD);
-              goto error;
-            }
-          } else if (parser->method == HTTP_LOCK) {
-            if (ch == 'I') {
-              parser->method = HTTP_LINK;
-            } else {
-              SET_ERRNO(HPE_INVALID_METHOD);
-              goto error;
-            }
-          }
-        } else if (parser->index == 2) {
-          if (parser->method == HTTP_PUT) {
-            if (ch == 'R') {
-              parser->method = HTTP_PURGE;
-            } else {
-              SET_ERRNO(HPE_INVALID_METHOD);
-              goto error;
-            }
-          } else if (parser->method == HTTP_UNLOCK) {
-            if (ch == 'S') {
-              parser->method = HTTP_UNSUBSCRIBE;
-            } else if(ch == 'B') {
-              parser->method = HTTP_UNBIND;
-            } else {
+        } else if (IS_ALPHA(ch)) {
+
+          switch (parser->method << 16 | parser->index << 8 | ch) {
+#define XX(meth, pos, ch, new_meth) \
+            case (HTTP_##meth << 16 | pos << 8 | ch): \
+              parser->method = HTTP_##new_meth; break;
+
+            XX(POST,      1, 'U', PUT)
+            XX(POST,      1, 'A', PATCH)
+            XX(CONNECT,   1, 'H', CHECKOUT)
+            XX(CONNECT,   2, 'P', COPY)
+            XX(MKCOL,     1, 'O', MOVE)
+            XX(MKCOL,     1, 'E', MERGE)
+            XX(MKCOL,     2, 'A', MKACTIVITY)
+            XX(MKCOL,     3, 'A', MKCALENDAR)
+            XX(SUBSCRIBE, 1, 'E', SEARCH)
+            XX(REPORT,    2, 'B', REBIND)
+            XX(POST,      1, 'R', PROPFIND)
+            XX(PROPFIND,  4, 'P', PROPPATCH)
+            XX(PUT,       2, 'R', PURGE)
+            XX(LOCK,      1, 'I', LINK)
+            XX(UNLOCK,    2, 'S', UNSUBSCRIBE)
+            XX(UNLOCK,    2, 'B', UNBIND)
+            XX(UNLOCK,    3, 'I', UNLINK)
+#undef XX
+
+            default:
               SET_ERRNO(HPE_INVALID_METHOD);
               goto error;
-            }
-          } else {
-            SET_ERRNO(HPE_INVALID_METHOD);
-            goto error;
           }
-        } else if (parser->index == 4 && parser->method == HTTP_PROPFIND && ch == 'P') {
-          parser->method = HTTP_PROPPATCH;
-        } else if (parser->index == 3 && parser->method == HTTP_UNLOCK && ch == 'I') {
-          parser->method = HTTP_UNLINK;
+        } else if (ch == '-' &&
+                   parser->index == 1 &&
+                   parser->method == HTTP_MKCOL) {
+          parser->method = HTTP_MSEARCH;
         } else {
           SET_ERRNO(HPE_INVALID_METHOD);
           goto error;