http: refacto http header parsing

src/http/Client.zig

@@ -309,6 +309,9 @@ fn makeRequest(self: *Client, handle: *Handle, transfer: *Transfer) !void {
         transfer._handle = handle;
         errdefer transfer.deinit();
 
+        // Store the proxy's information in transfer to ease headers parsing.
+        transfer._use_proxy = conn.opts.use_proxy;
+
         try conn.setURL(req.url);
         try conn.setMethod(req.method);
         if (req.body) |b| {
@@ -574,6 +577,13 @@ pub const Transfer = struct {
 
     _redirecting: bool = false,
 
+    // use_proxy is set when the transfer has been associated to a given
+    // connection in makeRequest().
+    _use_proxy: bool = undefined,
+
+    // stateful variables used to parse responses headers.
+    _resp_header_status: enum { empty, first, next, end } = .empty,
+
     fn deinit(self: *Transfer) void {
         self.req.headers.deinit();
         if (self._handle) |handle| {
@@ -684,20 +694,23 @@ pub const Transfer = struct {
 
         const header = buffer[0 .. buf_len - 2];
 
-        if (transfer.response_header == null) {
+        // transition the status dependending the previous one.
-            if (transfer._redirecting and buf_len == 2) {
+        transfer._resp_header_status = switch (transfer._resp_header_status) {
-                // parse and set cookies for the redirection.
+            .empty => .first,
-                redirectionCookies(transfer, easy) catch |err| {
+            .first => .next,
-                    log.debug(.http, "redirection cookies", .{ .err = err });
+            .next => .next,
-                    return 0;
+            .end => .first,
         };
-                return buf_len;
-            }
 
-            if (buf_len < 13 or std.mem.startsWith(u8, header, "HTTP/") == false) {
+        // mark the end of parsing headers
-                if (transfer._redirecting) {
+        if (buf_len == 2) transfer._resp_header_status = .end;
-                    return buf_len;
+
-                }
+        log.debug(.http, "header parsing", .{ .status = transfer._resp_header_status });
+
+        switch (transfer._resp_header_status) {
+            .empty => unreachable,
+            .first => {
+                if (buf_len < 13) {
                     log.debug(.http, "invalid response line", .{ .line = header });
                     return 0;
                 }
@@ -729,12 +742,19 @@ pub const Transfer = struct {
                     .url = url,
                     .status = status,
                 };
-            transfer.bytes_received = buf_len;
+            },
+            .next => {},
+            .end => {
+                // If we are in a redirection, take care of cookies only.
+                if (transfer._redirecting) {
+                    // parse and set cookies for the redirection.
+                    redirectionCookies(transfer, easy) catch |err| {
+                        log.debug(.http, "redirection cookies", .{ .err = err });
+                        return 0;
+                    };
                     return buf_len;
                 }
 
-        transfer.bytes_received += buf_len;
-        if (buf_len == 2) {
                 if (getResponseHeader(easy, "content-type", 0)) |ct| {
                     var hdr = &transfer.response_header.?;
                     const value = ct.value;
@@ -765,7 +785,10 @@ pub const Transfer = struct {
                         .transfer = transfer,
                     });
                 }
+            },
         }
+
+        transfer.bytes_received += buf_len;
         return buf_len;
     }