# HG changeset patch
# User Sergey Kandaurov <pluknet@nginx.com>
# Date 1621698045 -10800
# Node ID 81d491f0dc8cd8376ffd1dc3e990ab33ac0d9628
# Parent  557dc6a06ba6ea7e78444067c4b8fbb022f7b191
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
--- 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 
 }
 
 
-static ngx_uint_t
+static ngx_inline ngx_uint_t
 ngx_quic_varint_len(uint64_t value)
 {
-    ngx_uint_t  bits;
-
-    bits = 0;
-    while (value >> ((8 << bits) - 2)) {
-        bits++;
+    if (value < (1 << 6)) {
+        return 1;
+    }
+
+    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);
+
+    } else if (value < (1 << 14)) {
+        ngx_quic_build_int_set(p, value, 1, 1);
+        ngx_quic_build_int_set(p, value, 0, 0);
+
+    } 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);
     }
 
-    len = (1 << bits);
-
-    while (len--) {
-        *p++ = value >> (len * 8);
-    }
-
-    **pos |= bits << 6;
     *pos = p;
 }