VarInt decoding pseudocode

draft-ietf-quic-transport.md

@@ -4345,10 +4345,7 @@ encoding properties.
 | 11   | 8      | 62          | 0-4611686018427387903 |
 {: #integer-summary title="Summary of Integer Encodings"}
 
-For example, the eight byte sequence c2 19 7c 5e ff 14 e8 8c (in hexadecimal)
-decodes to the decimal value 151288809941952652; the four byte sequence 9d 7f 3e
-7d decodes to 494878333; the two byte sequence 7b bd decodes to 15293; and the
-single byte 25 decodes to 37 (as does the two byte sequence 40 25).
+Examples and a sample decoding algorithm are shown in {{sample-varint}}.
 
 Versions ({{versions}}) and packet numbers sent in the header
 ({{packet-encoding}}) are described using integers, but do not use this
@@ -7486,6 +7483,34 @@ ECN to be disabled.  For those rare cases where marked packets are discarded by
 the path, the short duration of the testing period limits the number of losses
 incurred.
 
+# Sample Variable-Length Integer Decoding {#sample-varint}
+
+The pseudo-code in {{alg-varint}} shows how a variable-length integer can be
+read from a stream of bytes.  The function ReadVarint takes a single argument, a
+sequence of bytes which can be read in network byte order.
+
+~~~
+ReadVarint(data):
+  // The length of variable-length integers is encoded in the
+  // first two bits of the first byte.
+  v = data.next_byte()
+  prefix = v >> 6
+  length = 1 << prefix
+
+  // Once the length is known, remove these bits and read any
+  // remaining bytes.
+  v = v & 0x3f
+  repeat length-1 times:
+    v = (v << 8) + data.next_byte()
+  return v
+~~~
+{: #alg-varint title="Sample Variable-Length Integer Decoding Algorithm"}
+
+For example, the eight-byte sequence 0xc2197c5eff14e88c decodes to the decimal
+value 151,288,809,941,952,652; the four-byte sequence 0x9d7f3e7d decodes to
+494,878,333; the two-byte sequence 0x7bbd decodes to 15,293; and the single byte
+0x25 decodes to 37 (as does the two-byte sequence 0x4025).
+
 
 
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