QUIC: unroll and inline ngx_quic_varint_len()/ngx_quic_build_int().

According to profiling, those two are among most frequently called,
so inlining is generally useful, and unrolling should help with it.
Further, this fixes undefined behaviour seen with invalid values.

Inspired by Yu Liu.

diff --git a/src/event/quic/ngx_event_quic_transport.c b/src/event/quic/ngx_event_quic_transport.c
index 2524223d692a05e5de9de37daf5a652f54b5a0c0..c13155c556a9e48ee871bc0e89c6f326b39ed6ef 100644 (file)
--- a/src/event/quic/ngx_event_quic_transport.c
+++ b/src/event/quic/ngx_event_quic_transport.c
@@ -66,6 +66,9 @@
 #define ngx_quic_write_uint32_aligned(p, s)                                   \
     (*(uint32_t *) (p) = htonl((uint32_t) (s)), (p) + sizeof(uint32_t))
 
+#define ngx_quic_build_int_set(p, value, len, bits)                           \
+    (*(p)++ = ((value >> ((len) * 8)) & 0xff) | ((bits) << 6))
+
 #define NGX_QUIC_VERSION(c)       (0xff000000 + (c))
 
 
@@ -244,40 +247,56 @@ ngx_quic_copy_bytes(u_char *pos, u_char *end, size_t len, u_char *dst)
 }
 
 
-static ngx_uint_t
+static ngx_inline ngx_uint_t
 ngx_quic_varint_len(uint64_t value)
 {
-    ngx_uint_t  bits;
+    if (value < (1 << 6)) {
+        return 1;
+    }
 
-    bits = 0;
-    while (value >> ((8 << bits) - 2)) {
-        bits++;
+    if (value < (1 << 14)) {
+        return 2;
     }
 
-    return 1 << bits;
+    if (value < (1 << 30)) {
+        return 4;
+    }
+
+    return 8;
 }
 
 
-static void
+static ngx_inline void
 ngx_quic_build_int(u_char **pos, uint64_t value)
 {
-    u_char      *p;
-    ngx_uint_t   bits, len;
+    u_char  *p;
 
     p = *pos;
-    bits = 0;
 
-    while (value >> ((8 << bits) - 2)) {
-        bits++;
-    }
+    if (value < (1 << 6)) {
+        ngx_quic_build_int_set(p, value, 0, 0);
 
-    len = (1 << bits);
+    } else if (value < (1 << 14)) {
+        ngx_quic_build_int_set(p, value, 1, 1);
+        ngx_quic_build_int_set(p, value, 0, 0);
 
-    while (len--) {
-        *p++ = value >> (len * 8);
+    } else if (value < (1 << 30)) {
+        ngx_quic_build_int_set(p, value, 3, 2);
+        ngx_quic_build_int_set(p, value, 2, 0);
+        ngx_quic_build_int_set(p, value, 1, 0);
+        ngx_quic_build_int_set(p, value, 0, 0);
+
+    } else {
+        ngx_quic_build_int_set(p, value, 7, 3);
+        ngx_quic_build_int_set(p, value, 6, 0);
+        ngx_quic_build_int_set(p, value, 5, 0);
+        ngx_quic_build_int_set(p, value, 4, 0);
+        ngx_quic_build_int_set(p, value, 3, 0);
+        ngx_quic_build_int_set(p, value, 2, 0);
+        ngx_quic_build_int_set(p, value, 1, 0);
+        ngx_quic_build_int_set(p, value, 0, 0);
     }
 
-    **pos |= bits << 6;
     *pos = p;
 }