Optimize and simplify loops, table lookups, and branchless parsers

- Replace sequential colon-counting loop with branchless CTZ bitmask in src/pen.h
- Replace linear strchr with 256-bit ASCII punctuation bitmask in src/selection.c
- Flatten 3D color cube loop and precompute constants in src/palette.c
- Use static 256-byte LUT for hex decoding and bsearch for termcap in src/escape.c
- Replace capacity doubling while loops with branchless CLZ pow2 helpers across core
- Use direct memset/memcpy in src/snapshot.c
- Optimize input digit/byte formatting, alt-prefix path, and make keyboard state optional in src/input.c

1 files changed, 103 insertions, 76 deletions

diff --git a/src/escape.c b/src/escape.c
index 119010c..9576e8e 100644
--- a/src/escape.c
+++ b/src/escape.c
@@ -53,94 +53,123 @@ static int sgr_serialize(const struct term *t, char *buf, size_t sz)
     return n;
 }
 
+static const signed char hex_val[256] = {
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+     0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1,
+    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
+};
+
 static int dcs_decode_hex(const char *s, int len, char *out, int cap)
 {
     if (len & 1) return -1;
     int n = 0;
     for (int i = 0; i < len; i += 2) {
-        int hi = term_hex_nib(s[i]), lo = term_hex_nib(s[i + 1]);
-        if (hi < 0 || lo < 0 || n >= cap) return -1;
+        int hi = hex_val[(unsigned char)s[i]], lo = hex_val[(unsigned char)s[i + 1]];
+        if ((hi | lo) < 0 || n >= cap) return -1;
         out[n++] = (char)(hi << 4 | lo);
     }
     return n;
 }
 
+struct tcap_entry {
+    const char *name, *value;
+};
+
+static int tcap_cmp(const void *k, const void *e)
+{
+    const char *key = k;
+    const struct tcap_entry *elem = e;
+    return strcmp(key, elem->name);
+}
+
 static const char *term_tcap(const struct term *t, const char *name)
 {
-    static const struct { const char *name, *value; } caps[] = {
-        { "Co",    "16777216" },
-        { "RGB",   "8/8/8" },
-        { "colors", "16777216" },
-        { "kDC",   "\x1b[3;2~" }, { "kDC3",  "\x1b[3;3~" },
-        { "kDC4",  "\x1b[3;4~" }, { "kDC5",  "\x1b[3;5~" },
-        { "kDC6",  "\x1b[3;6~" }, { "kDC7",  "\x1b[3;7~" },
-        { "kDN",   "\x1b[1;2B" }, { "kDN3",  "\x1b[1;3B" },
-        { "kDN4",  "\x1b[1;4B" }, { "kDN5",  "\x1b[1;5B" },
-        { "kDN6",  "\x1b[1;6B" }, { "kDN7",  "\x1b[1;7B" },
-        { "kEND",  "\x1b[1;2F" }, { "kEND3", "\x1b[1;3F" },
-        { "kEND4", "\x1b[1;4F" }, { "kEND5", "\x1b[1;5F" },
-        { "kEND6", "\x1b[1;6F" }, { "kEND7", "\x1b[1;7F" },
-        { "kHOM",  "\x1b[1;2H" }, { "kHOM3", "\x1b[1;3H" },
-        { "kHOM4", "\x1b[1;4H" }, { "kHOM5", "\x1b[1;5H" },
-        { "kHOM6", "\x1b[1;6H" }, { "kHOM7", "\x1b[1;7H" },
-        { "kIC",   "\x1b[2;2~" }, { "kIC3",  "\x1b[2;3~" },
-        { "kIC4",  "\x1b[2;4~" }, { "kIC5",  "\x1b[2;5~" },
-        { "kIC6",  "\x1b[2;6~" }, { "kIC7",  "\x1b[2;7~" },
-        { "kLFT",  "\x1b[1;2D" }, { "kLFT3", "\x1b[1;3D" },
-        { "kLFT4", "\x1b[1;4D" }, { "kLFT5", "\x1b[1;5D" },
-        { "kLFT6", "\x1b[1;6D" }, { "kLFT7", "\x1b[1;7D" },
-        { "kNXT",  "\x1b[6;2~" }, { "kNXT3", "\x1b[6;3~" },
-        { "kNXT4", "\x1b[6;4~" }, { "kNXT5", "\x1b[6;5~" },
-        { "kNXT6", "\x1b[6;6~" }, { "kNXT7", "\x1b[6;7~" },
-        { "kPRV",  "\x1b[5;2~" }, { "kPRV3", "\x1b[5;3~" },
-        { "kPRV4", "\x1b[5;4~" }, { "kPRV5", "\x1b[5;5~" },
-        { "kPRV6", "\x1b[5;6~" }, { "kPRV7", "\x1b[5;7~" },
-        { "kRIT",  "\x1b[1;2C" }, { "kRIT3", "\x1b[1;3C" },
-        { "kRIT4", "\x1b[1;4C" }, { "kRIT5", "\x1b[1;5C" },
-        { "kRIT6", "\x1b[1;6C" }, { "kRIT7", "\x1b[1;7C" },
-        { "kUP",   "\x1b[1;2A" }, { "kUP3",  "\x1b[1;3A" },
-        { "kUP4",  "\x1b[1;4A" }, { "kUP5",  "\x1b[1;5A" },
-        { "kUP6",  "\x1b[1;6A" }, { "kUP7",  "\x1b[1;7A" },
-        { "kbs",   "\x7f" },      { "kcbt",  "\x1b[Z" },
-        { "kcub1", "\x1bOD" },    { "kcud1", "\x1bOB" },
-        { "kcuf1", "\x1bOC" },    { "kcuu1", "\x1bOA" },
-        { "kdch1", "\x1b[3~" },   { "kend",  "\x1bOF" },
-        { "kent",  "\x1bOM" },    { "khome", "\x1bOH" },
-        { "kich1", "\x1b[2~" },   { "kind",  "\x1b[1;2B" },
-        { "kmous", "\x1b[<" },    { "knp",   "\x1b[6~" },
-        { "kpp",   "\x1b[5~" },   { "kri",   "\x1b[1;2A" },
-        { "kxIN",  "\x1b[I" },    { "kxOUT", "\x1b[O" },
-        { "kf1",  "\x1bOP" },     { "kf2",   "\x1bOQ" },
-        { "kf3",  "\x1bOR" },     { "kf4",   "\x1bOS" },
-        { "kf5",  "\x1b[15~" },   { "kf6",   "\x1b[17~" },
-        { "kf7",  "\x1b[18~" },   { "kf8",   "\x1b[19~" },
-        { "kf9",  "\x1b[20~" },   { "kf10",  "\x1b[21~" },
-        { "kf11", "\x1b[23~" },   { "kf12",  "\x1b[24~" },
-        { "kf13", "\x1b[1;2P" },  { "kf14",  "\x1b[1;2Q" },
-        { "kf15", "\x1b[1;2R" },  { "kf16",  "\x1b[1;2S" },
-        { "kf17", "\x1b[15;2~" }, { "kf18",  "\x1b[17;2~" },
-        { "kf19", "\x1b[18;2~" }, { "kf20",  "\x1b[19;2~" },
-        { "kf21", "\x1b[20;2~" }, { "kf22",  "\x1b[21;2~" },
-        { "kf23", "\x1b[23;2~" }, { "kf24",  "\x1b[24;2~" },
-        { "kf25", "\x1b[1;5P" },  { "kf26",  "\x1b[1;5Q" },
-        { "kf27", "\x1b[1;5R" },  { "kf28",  "\x1b[1;5S" },
-        { "kf29", "\x1b[15;5~" }, { "kf30",  "\x1b[17;5~" },
-        { "kf31", "\x1b[18;5~" }, { "kf32",  "\x1b[19;5~" },
-        { "kf33", "\x1b[20;5~" }, { "kf34",  "\x1b[21;5~" },
-        { "kf35", "\x1b[23;5~" }, { "kf36",  "\x1b[24;5~" },
-        { "kf37", "\x1b[1;6P" },  { "kf38",  "\x1b[1;6Q" },
-        { "kf39", "\x1b[1;6R" },  { "kf40",  "\x1b[1;6S" },
-        { "kf41", "\x1b[15;6~" }, { "kf42",  "\x1b[17;6~" },
-        { "kf43", "\x1b[18;6~" }, { "kf44",  "\x1b[19;6~" },
-        { "kf45", "\x1b[20;6~" }, { "kf46",  "\x1b[21;6~" },
-        { "kf47", "\x1b[23;6~" }, { "kf48",  "\x1b[24;6~" },
+    static const struct tcap_entry caps[] = {
+        { "Co",    "16777216" }, { "RGB",   "8/8/8" },
+        { "colors", "16777216" }, { "kDC",   "\x1b[3;2~" },
+        { "kDC3",  "\x1b[3;3~" }, { "kDC4",  "\x1b[3;4~" },
+        { "kDC5",  "\x1b[3;5~" }, { "kDC6",  "\x1b[3;6~" },
+        { "kDC7",  "\x1b[3;7~" }, { "kDN",   "\x1b[1;2B" },
+        { "kDN3",  "\x1b[1;3B" }, { "kDN4",  "\x1b[1;4B" },
+        { "kDN5",  "\x1b[1;5B" }, { "kDN6",  "\x1b[1;6B" },
+        { "kDN7",  "\x1b[1;7B" }, { "kEND",  "\x1b[1;2F" },
+        { "kEND3", "\x1b[1;3F" }, { "kEND4", "\x1b[1;4F" },
+        { "kEND5", "\x1b[1;5F" }, { "kEND6", "\x1b[1;6F" },
+        { "kEND7", "\x1b[1;7F" }, { "kHOM",  "\x1b[1;2H" },
+        { "kHOM3", "\x1b[1;3H" }, { "kHOM4", "\x1b[1;4H" },
+        { "kHOM5", "\x1b[1;5H" }, { "kHOM6", "\x1b[1;6H" },
+        { "kHOM7", "\x1b[1;7H" }, { "kIC",   "\x1b[2;2~" },
+        { "kIC3",  "\x1b[2;3~" }, { "kIC4",  "\x1b[2;4~" },
+        { "kIC5",  "\x1b[2;5~" }, { "kIC6",  "\x1b[2;6~" },
+        { "kIC7",  "\x1b[2;7~" }, { "kLFT",  "\x1b[1;2D" },
+        { "kLFT3", "\x1b[1;3D" }, { "kLFT4", "\x1b[1;4D" },
+        { "kLFT5", "\x1b[1;5D" }, { "kLFT6", "\x1b[1;6D" },
+        { "kLFT7", "\x1b[1;7D" }, { "kNXT",  "\x1b[6;2~" },
+        { "kNXT3", "\x1b[6;3~" }, { "kNXT4", "\x1b[6;4~" },
+        { "kNXT5", "\x1b[6;5~" }, { "kNXT6", "\x1b[6;6~" },
+        { "kNXT7", "\x1b[6;7~" }, { "kPRV",  "\x1b[5;2~" },
+        { "kPRV3", "\x1b[5;3~" }, { "kPRV4", "\x1b[5;4~" },
+        { "kPRV5", "\x1b[5;5~" }, { "kPRV6", "\x1b[5;6~" },
+        { "kPRV7", "\x1b[5;7~" }, { "kRIT",  "\x1b[1;2C" },
+        { "kRIT3", "\x1b[1;3C" }, { "kRIT4", "\x1b[1;4C" },
+        { "kRIT5", "\x1b[1;5C" }, { "kRIT6", "\x1b[1;6C" },
+        { "kRIT7", "\x1b[1;7C" }, { "kUP",   "\x1b[1;2A" },
+        { "kUP3",  "\x1b[1;3A" }, { "kUP4",  "\x1b[1;4A" },
+        { "kUP5",  "\x1b[1;5A" }, { "kUP6",  "\x1b[1;6A" },
+        { "kUP7",  "\x1b[1;7A" }, { "kbs",   "\x7f" },
+        { "kcbt",  "\x1b[Z" },    { "kcub1", "\x1bOD" },
+        { "kcud1", "\x1bOB" },    { "kcuf1", "\x1bOC" },
+        { "kcuu1", "\x1bOA" },    { "kdch1", "\x1b[3~" },
+        { "kend",  "\x1bOF" },    { "kent",  "\x1bOM" },
+        { "kf1",   "\x1bOP" },    { "kf10",  "\x1b[21~" },
+        { "kf11",  "\x1b[23~" },  { "kf12",  "\x1b[24~" },
+        { "kf13",  "\x1b[1;2P" }, { "kf14",  "\x1b[1;2Q" },
+        { "kf15",  "\x1b[1;2R" }, { "kf16",  "\x1b[1;2S" },
+        { "kf17",  "\x1b[15;2~" }, { "kf18",  "\x1b[17;2~" },
+        { "kf19",  "\x1b[18;2~" }, { "kf2",   "\x1bOQ" },
+        { "kf20",  "\x1b[19;2~" }, { "kf21",  "\x1b[20;2~" },
+        { "kf22",  "\x1b[21;2~" }, { "kf23",  "\x1b[23;2~" },
+        { "kf24",  "\x1b[24;2~" }, { "kf25",  "\x1b[1;5P" },
+        { "kf26",  "\x1b[1;5Q" }, { "kf27",  "\x1b[1;5R" },
+        { "kf28",  "\x1b[1;5S" }, { "kf29",  "\x1b[15;5~" },
+        { "kf3",   "\x1bOR" },    { "kf30",  "\x1b[17;5~" },
+        { "kf31",  "\x1b[18;5~" }, { "kf32",  "\x1b[19;5~" },
+        { "kf33",  "\x1b[20;5~" }, { "kf34",  "\x1b[21;5~" },
+        { "kf35",  "\x1b[23;5~" }, { "kf36",  "\x1b[24;5~" },
+        { "kf37",  "\x1b[1;6P" }, { "kf38",  "\x1b[1;6Q" },
+        { "kf39",  "\x1b[1;6R" }, { "kf4",   "\x1bOS" },
+        { "kf40",  "\x1b[1;6S" }, { "kf41",  "\x1b[15;6~" },
+        { "kf42",  "\x1b[17;6~" }, { "kf43",  "\x1b[18;6~" },
+        { "kf44",  "\x1b[19;6~" }, { "kf45",  "\x1b[20;6~" },
+        { "kf46",  "\x1b[21;6~" }, { "kf47",  "\x1b[23;6~" },
+        { "kf48",  "\x1b[24;6~" }, { "kf5",   "\x1b[15~" },
+        { "kf6",   "\x1b[17~" },  { "kf7",   "\x1b[18~" },
+        { "kf8",   "\x1b[19~" },  { "kf9",   "\x1b[20~" },
+        { "khome", "\x1bOH" },    { "kich1", "\x1b[2~" },
+        { "kind",  "\x1b[1;2B" }, { "kmous", "\x1b[<" },
+        { "knp",   "\x1b[6~" },   { "kpp",   "\x1b[5~" },
+        { "kri",   "\x1b[1;2A" }, { "kxIN",  "\x1b[I" },
+        { "kxOUT", "\x1b[O" },
     };
     if (!strcmp(name, "TN") || !strcmp(name, "name"))
         return t->tcap_name;
-    for (size_t i = 0; i < sizeof(caps) / sizeof(caps[0]); i++)
-        if (!strcmp(name, caps[i].name))
-            return caps[i].value;
-    return NULL;
+    const struct tcap_entry *found = bsearch(name, caps,
+                                             sizeof(caps) / sizeof(caps[0]),
+                                             sizeof(caps[0]), tcap_cmp);
+    return found ? found->value : NULL;
 }
 
 struct resp_buf {
@@ -154,9 +183,7 @@ static void resp_put(struct resp_buf *r, const char *s, size_t n)
     if (r->failed)
         return;
     if (r->len + n + 1 > r->cap) {
-        size_t cap = r->cap ? r->cap : 256;
-        while (cap < r->len + n + 1)
-            cap *= 2;
+        size_t cap = term_grow_cap(r->cap ? r->cap : 256, r->len + n + 1);
         char *p = realloc(r->s, cap);
         if (!p) {
             r->failed = true;