200 line symbol table implementation and the first commit

Setup build system (POSIX sh), gitignore, basic C file with an
implementation of something I really wanted to setup.

It just hashes a snippet of lorem ipsum.  Testing seems to indicate
it's working. That's all it does lol.

This is a really pressing matter; all my previous Lisps always just
made the strings on the fly and that irked me deeply.  I want a smart
implementation that really tries to save memory on something as
intensive as symbols.

.dir-locals.el

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+;;; Directory Local Variables            -*- no-byte-compile: t -*-
+;;; For more information see (info "(emacs) Directory Variables")
+
+((nil . ((compile-command . "sh build.sh")
+         (+license/license-choice . "Unlicense")))
+ (c-mode . ((mode . clang-format))))

.gitignore

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+*.o
+*.out
+.cache/
+compile_commands.json
+TAGS

LICENSE

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+This is free and unencumbered software released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or
+distribute this software, either in source code form or as a compiled
+binary, for any purpose, commercial or non-commercial, and by any
+means.
+
+In jurisdictions that recognize copyright laws, the author or authors
+of this software dedicate any and all copyright interest in the
+software to the public domain. We make this dedication for the benefit
+of the public at large and to the detriment of our heirs and
+successors. We intend this dedication to be an overt act of
+relinquishment in perpetuity of all present and future rights to this
+software under copyright law.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+For more information, please refer to <https://unlicense.org>

build.sh

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+#!/usr/bin/env sh
+
+CFLAGS="-Wall -Wextra -std=c11 -ggdb"
+SRC="main.c"
+OUT="main.out"
+
+set -xe
+
+cc $CFLAGS -o $OUT $SRC;

main.c

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+/* Copyright (C) 2025 Aryadev Chavali
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the Unlicense
+ * for details.
+
+ * You may distribute and modify this code under the terms of the
+ * Unlicense, which you should have received a copy of along with this
+ * program.  If not, please go to <https://unlicense.org/>.
+
+ * Created: 2025-08-19
+ * Description: Entrypoint
+ */
+
+#include <malloc.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#define MAX(A, B) ((A) > (B) ? (A) : (B))
+#define MIN(A, B) ((A) < (B) ? (A) : (B))
+
+typedef uint8_t u8;
+typedef uint16_t u16;
+typedef uint32_t u32;
+typedef uint64_t u64;
+
+typedef int8_t i8;
+typedef int16_t i16;
+typedef int32_t i32;
+typedef int64_t i64;
+
+typedef struct
+{
+  u64 size, capacity;
+  u8 bytes[];
+} vec_t;
+
+#define VEC_GET(P)  (((vec_t *)(P)) - 1)
+#define VEC_SIZE(P) (VEC_GET(P)->size)
+#define VEC_CAP(P)  (VEC_GET(P)->capacity)
+#define VEC_MULT    2
+
+void vec_make(void **ptr, u64 size)
+{
+  if (!ptr)
+    return;
+  vec_t *vector    = calloc(1, sizeof(*vector) + size);
+  vector->size     = 0;
+  vector->capacity = size;
+  *ptr             = (vector + 1);
+}
+
+void vec_free(void **data)
+{
+  if (!data || !*data)
+    return;
+  free(VEC_GET(*data));
+  *data = NULL;
+}
+
+void vec_ensure_remaining(void **ptr, u64 space)
+{
+  if (!ptr || !*ptr)
+    return;
+  vec_t *vec = VEC_GET(*ptr);
+  if (vec->capacity - vec->size < space)
+  {
+    void *new_vec = NULL;
+    vec_make(&new_vec, MAX(vec->capacity * VEC_MULT, vec->size + space));
+    VEC_SIZE(new_vec) = vec->size;
+    memcpy(new_vec, *ptr, vec->size);
+    vec_free(ptr);
+    *ptr = new_vec;
+  }
+}
+
+void vec_append_byte(void **ptr, u8 byte)
+{
+  vec_ensure_remaining(ptr, 1);
+  vec_t *vec              = VEC_GET(*ptr);
+  vec->bytes[vec->size++] = byte;
+}
+
+void vec_append(void **ptr, void *data, u64 size)
+{
+  vec_ensure_remaining(ptr, size);
+  vec_t *vec = VEC_GET(*ptr);
+  memcpy(*ptr + vec->size, data, size);
+  vec->size += size;
+}
+
+void vec_clone(void **dest, void **src)
+{
+  if (!dest || !src || !*src)
+    return;
+  vec_make(dest, VEC_SIZE(*src));
+  memcpy(*dest, *src, VEC_SIZE(*src));
+  VEC_SIZE(*dest) = VEC_SIZE(*src);
+}
+
+typedef struct
+{
+  u64 size;
+  char *data;
+} sv_t;
+
+#define SV(DATA, SIZE) ((sv_t){.data = (DATA), .size = (SIZE)})
+#define SV_FMT(SV)     (int)(SV).size, (SV).data
+#define PR_SV          "%.*s"
+
+sv_t sv_copy(sv_t old)
+{
+  char *newstr = calloc(1, old.size * sizeof(*newstr));
+  memcpy(newstr, old.data, old.size);
+  return SV(newstr, old.size);
+}
+
+typedef struct
+{
+  u64 count;     // How many strings?
+  u64 capacity;  // How many entry buckets?
+  sv_t *entries; // this is actually a vector on the inside lol
+} sym_table_t;
+
+u64 djb2(sv_t string)
+{
+  u64 hash = 5381;
+  for (u64 i = 0; i < string.size; ++i)
+    hash = string.data[i] + (hash + (hash << 5));
+  return hash;
+}
+
+#define SYM_TABLE_INIT_SIZE 1024
+
+void sym_table_init(sym_table_t *table)
+{
+  table->capacity = MAX(table->capacity, SYM_TABLE_INIT_SIZE);
+  table->count    = 0;
+  vec_make((void **)&table->entries, table->capacity * sizeof(*table->entries));
+}
+
+sv_t sym_table_find(sym_table_t *table, sv_t sv)
+{
+  // TODO: Deal with resizing this when table->count > table->size / 2
+  u64 index = djb2(sv) & (table->capacity - 1);
+
+  for (sv_t comp  = table->entries[index]; comp.data; index += 1,
+            index = index & (table->capacity - 1), comp = table->entries[index])
+    // Is it present in the table?
+    if (sv.size == comp.size && strncmp(sv.data, comp.data, sv.size) == 0)
+      return comp;
+
+  // Otherwise we need to duplicate and make it permanently interned
+  sv_t newsv            = sv_copy(sv);
+  table->entries[index] = newsv;
+  ++table->count;
+
+  return newsv;
+}
+
+void sym_table_cleanup(sym_table_t *table)
+{
+  for (u64 i = 0; i < table->capacity; ++i)
+    if (table->entries[i].data)
+      free(table->entries[i].data);
+  vec_free((void **)&table->entries);
+  memset(table, 0, sizeof(*table));
+}
+
+int main(void)
+{
+  sym_table_t table = {0};
+  sym_table_init(&table);
+  // Let's hash the words of lorem ipsum
+  const char *words[] = {
+      "aliquam",      "erat",      "volutpat",  "nunc",      "eleifend",
+      "leo",          "vitae",     "magna",     "in",        "id",
+      "erat",         "non",       "orci",      "commodo",   "lobortis",
+      "proin",        "neque",     "massa",     "cursus",    "ut",
+      "gravida",      "ut",        "lobortis",  "eget",      "lacus",
+      "sed",          "diam",      "praesent",  "fermentum", "tempor",
+      "tellus",       "nullam",    "tempus",    "mauris",    "ac",
+      "felis",        "vel",       "velit",     "tristique", "imperdiet",
+      "donec",        "at",        "pede",      "etiam",     "vel",
+      "neque",        "nec",       "dui",       "dignissim", "bibendum",
+      "vivamus",      "id",        "enim",      "phasellus", "neque",
+      "orci",         "porta",     "a",         "aliquet",   "quis",
+      "semper",       "a",         "massa",     "phasellus", "purus",
+      "pellentesque", "tristique", "imperdiet", "tortor",    "nam",
+      "euismod",      "tellus",    "id",        "erat",
+  };
+
+  for (u64 i = 0; i < sizeof(words) / sizeof(words[0]); ++i)
+  {
+    sv_t sv = sym_table_find(&table, SV(words[i], strlen(words[i])));
+    printf("%s => %p\n", words[i], sv.data);
+  }
+  return 0;
+}