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Fri, 31 Jul 2026 03:38:16 -0400 (EDT) From: Junio C Hamano To: "brian m. carlson" Cc: Subject: Re: [RFC PATCH 1/6] hex: add functionality for lowercase-only hex In-Reply-To: <20260729233215.398654-2-sandals@crustytoothpaste.net> (brian m. carlson's message of "Wed, 29 Jul 2026 23:32:10 +0000") References: <20260729233215.398654-1-sandals@crustytoothpaste.net> <20260729233215.398654-2-sandals@crustytoothpaste.net> Date: Fri, 31 Jul 2026 00:38:14 -0700 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain "brian m. carlson" writes: > We currently allow both upper and lower case for all hex values in Git. > However, in a future commit, we'll want to change that to allow only > lowercase values in some cases. To prepare for that case, provide a > table to convert hex values using lowercase only and an enum to let us > choose which we want, wiring it up to the hexval function. > > For now, keep things completely the same by specifying only the > variant that accepts both lowercase and uppercase to avoid changing > behavior. > > Signed-off-by: brian m. carlson > --- In "some" cases? I wonder what other cases there are that we MUST accept uppercase variants. Obviously the network protocol where we are willing to talk to reimplementation of Git by others is one. I do not think we historically produced anything in uppercase. > diff --git a/color.c b/color.c > index 00b53f97ac..9015d0faf1 100644 > --- a/color.c > +++ b/color.c > @@ -72,7 +72,7 @@ static int get_hex_color(const char **inp, int width, unsigned char *out) > unsigned int val; > > assert(width == 1 || width == 2); > - val = (hexval(in[0]) << 4) | hexval(in[width - 1]); > + val = (hexval(in[0], HEX_KIND_MIXED) << 4) | hexval(in[width - 1], HEX_KIND_MIXED); > if (val & ~0xff) > return -1; > *inp += width; > diff --git a/hex-ll.c b/hex-ll.c > index 4d7ece1de5..fa85e91827 100644 > --- a/hex-ll.c > +++ b/hex-ll.c > @@ -36,10 +36,45 @@ const signed char hexval_table[256] = { > -1, -1, -1, -1, -1, -1, -1, -1, /* f8-ff */ > }; > > +const signed char hexval_lc_table[256] = { > + -1, -1, -1, -1, -1, -1, -1, -1, /* 00-07 */ > + -1, -1, -1, -1, -1, -1, -1, -1, /* 08-0f */ > + -1, -1, -1, -1, -1, -1, -1, -1, /* 10-17 */ > + -1, -1, -1, -1, -1, -1, -1, -1, /* 18-1f */ > + -1, -1, -1, -1, -1, -1, -1, -1, /* 20-27 */ > + -1, -1, -1, -1, -1, -1, -1, -1, /* 28-2f */ > + 0, 1, 2, 3, 4, 5, 6, 7, /* 30-37 */ > + 8, 9, -1, -1, -1, -1, -1, -1, /* 38-3f */ > + -1, -1, -1, -1, -1, -1, -1, -1, /* 40-47 */ > + -1, -1, -1, -1, -1, -1, -1, -1, /* 48-4f */ > + -1, -1, -1, -1, -1, -1, -1, -1, /* 50-57 */ > + -1, -1, -1, -1, -1, -1, -1, -1, /* 58-5f */ > + -1, 10, 11, 12, 13, 14, 15, -1, /* 60-67 */ > ... > + -1, -1, -1, -1, -1, -1, -1, -1, /* f8-ff */ > +}; > + > int hex_to_bytes(unsigned char *binary, const char *hex, size_t len) > { > for (; len; len--, hex += 2) { > - unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]); > + unsigned int val = (hexval(hex[0], HEX_KIND_MIXED) << 4) | hexval(hex[1], HEX_KIND_MIXED); > > if (val & ~0xff) > return -1; > > diff --git a/hex-ll.h b/hex-ll.h > index a381fa8556..da1b5239b2 100644 > --- a/hex-ll.h > +++ b/hex-ll.h > @@ -1,10 +1,16 @@ > #ifndef HEX_LL_H > #define HEX_LL_H > > +enum hexkind { > + HEX_KIND_MIXED = 0, > + HEX_KIND_LOWER = 1, > +}; > + > extern const signed char hexval_table[256]; > -static inline unsigned int hexval(unsigned char c) > +extern const signed char hexval_lc_table[256]; > +static inline unsigned int hexval(unsigned char c, enum hexkind kind) > { > - return hexval_table[c]; > + return kind == HEX_KIND_MIXED ? hexval_table[c] : hexval_lc_table[c]; > } It is very welcome to make sure we are conservative in what we produce, but be liberal in what we accept. In that sense, use of HEX_KIND_LOWER goes directly against the Robustness Principle. > > /* > @@ -13,8 +19,8 @@ static inline unsigned int hexval(unsigned char c) > */ > static inline int hex2chr(const char *s) > { > - unsigned int val = hexval(s[0]); > - return (val & ~0xf) ? val : (val << 4) | hexval(s[1]); > + unsigned int val = hexval(s[0], HEX_KIND_MIXED); > + return (val & ~0xf) ? val : (val << 4) | hexval(s[1], HEX_KIND_MIXED); > } > > /* > diff --git a/pkt-line.c b/pkt-line.c > index 3fc3e9ea70..338075558c 100644 > --- a/pkt-line.c > +++ b/pkt-line.c > @@ -378,10 +378,10 @@ int packet_length(const char lenbuf_hex[4], size_t size) > { > if (size < 4) > BUG("buffer too small"); > - return hexval(lenbuf_hex[0]) << 12 | > - hexval(lenbuf_hex[1]) << 8 | > - hexval(lenbuf_hex[2]) << 4 | > - hexval(lenbuf_hex[3]); > + return hexval(lenbuf_hex[0], HEX_KIND_MIXED) << 12 | > + hexval(lenbuf_hex[1], HEX_KIND_MIXED) << 8 | > + hexval(lenbuf_hex[2], HEX_KIND_MIXED) << 4 | > + hexval(lenbuf_hex[3], HEX_KIND_MIXED); > } > > static const char *find_packfile_uri_path(const char *buffer)