feat: added hash table implementation

core/src/CMakeLists.txt

@@ -1,4 +1,5 @@
 set(CORE_SRC
+  hash_table.c
   http_server.c
   core.c
 )

core/src/hash_table.c

@@ -0,0 +1,255 @@
+/**
+ * @file hash_table.c
+ * @brief Implementation of a hash table using CRC32 as the hash function.
+ *
+ * This file provides a hash table implementation with linear probing
+ * for collision resolution. It uses a CRC32 algorithm (derived from zlib)
+ * to compute hash values for string keys. The hash table supports
+ * insertion, retrieval, and resizing, with basic error handling.
+ *
+ * @note The CRC32 implementation is derived from zlib (Copyright 1995-1998 Mark
+ * Adler) and is subject to the conditions of the zlib license.
+ */
+
+#include "hash_table.h"
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+
+/* crc32.c -- compute the CRC-32 of a data stream
+ * Copyright (C) 1995-1998 Mark Adler
+ * For conditions of distribution and use, see copyright notice in zlib.h
+ */
+
+static const uint32_t crc_table[256] = {
+    0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L,
+    0x706af48fL, 0xe963a535L, 0x9e6495a3L, 0x0edb8832L, 0x79dcb8a4L,
+    0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L,
+    0x90bf1d91L, 0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL,
+    0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L, 0x136c9856L,
+    0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L,
+    0xfa0f3d63L, 0x8d080df5L, 0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L,
+    0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
+    0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L,
+    0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L, 0x26d930acL, 0x51de003aL,
+    0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L,
+    0xb8bda50fL, 0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L,
+    0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL, 0x76dc4190L,
+    0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL,
+    0x9fbfe4a5L, 0xe8b8d433L, 0x7807c9a2L, 0x0f00f934L, 0x9609a88eL,
+    0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
+    0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL,
+    0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L, 0x65b0d9c6L, 0x12b7e950L,
+    0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L,
+    0xfbd44c65L, 0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L,
+    0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL, 0x4369e96aL,
+    0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L,
+    0xaa0a4c5fL, 0xdd0d7cc9L, 0x5005713cL, 0x270241aaL, 0xbe0b1010L,
+    0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
+    0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L,
+    0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL, 0xedb88320L, 0x9abfb3b6L,
+    0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L,
+    0x73dc1683L, 0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L,
+    0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L, 0xf00f9344L,
+    0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL,
+    0x196c3671L, 0x6e6b06e7L, 0xfed41b76L, 0x89d32be0L, 0x10da7a5aL,
+    0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
+    0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L,
+    0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL, 0xd80d2bdaL, 0xaf0a1b4cL,
+    0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL,
+    0x4669be79L, 0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L,
+    0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL, 0xc5ba3bbeL,
+    0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L,
+    0x2cd99e8bL, 0x5bdeae1dL, 0x9b64c2b0L, 0xec63f226L, 0x756aa39cL,
+    0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
+    0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL,
+    0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L, 0x86d3d2d4L, 0xf1d4e242L,
+    0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L,
+    0x18b74777L, 0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL,
+    0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L, 0xa00ae278L,
+    0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L,
+    0x4969474dL, 0x3e6e77dbL, 0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L,
+    0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
+    0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L,
+    0xcdd70693L, 0x54de5729L, 0x23d967bfL, 0xb3667a2eL, 0xc4614ab8L,
+    0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL,
+    0x2d02ef8dL};
+
+#define DO1(buf) crc = crc_table[((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8);
+#define DO2(buf)                                                               \
+  DO1(buf);                                                                    \
+  DO1(buf);
+#define DO4(buf)                                                               \
+  DO2(buf);                                                                    \
+  DO2(buf);
+#define DO8(buf)                                                               \
+  DO4(buf);                                                                    \
+  DO4(buf);
+
+/**
+ * @brief Compute CRC-32 checksum of a data buffer.
+ *
+ * This function calculates the CRC-32 (Cyclic Redundancy Check) of the given
+ * buffer using the standard polynomial 0xEDB88320. It is derived from the
+ * zlib implementation.
+ *
+ * @param buffer Pointer to the data buffer.
+ * @param len    Length of the buffer in bytes.
+ * @return       The computed CRC-32 value.
+ */
+uint32_t crc32(const uint8_t *buffer, uint32_t len) {
+  uint32_t crc;
+  crc = 0;
+  crc = crc ^ 0xffffffffL;
+  while (len >= 8) {
+    DO8(buffer);
+    len -= 8;
+  }
+  if (len)
+    do {
+      DO1(buffer);
+    } while (--len);
+  return crc ^ 0xffffffffL;
+}
+
+/**
+ * @brief Initialize a new hash table.
+ *
+ * Allocates memory for a hash table and its internal element array.
+ * The table is initially empty with all slots marked as unused.
+ *
+ * @param size The number of slots in the hash table.
+ * @return     Pointer to the newly created hash table, or NULL if allocation
+ * fails.
+ */
+hash_table_p hash_table_init(size_t size) {
+  hash_table_p table;
+
+  table = (hash_table_p)calloc(1, sizeof(hash_table_t));
+  if (!table) {
+    return NULL;
+  }
+
+  table->elements = (hash_elem_t *)calloc(size, sizeof(hash_elem_t));
+  if (!table->elements) {
+    free(table);
+    return NULL;
+  }
+
+  table->size = size;
+
+  return table;
+}
+
+/**
+ * @brief Retrieve and clear the last error code.
+ *
+ * Returns the current error code stored in the hash table and resets it to
+ * HT_NONE. This allows the caller to check for errors after operations.
+ *
+ * @param hash_table Pointer to the hash table.
+ * @return           The error code (hash_table_error_e).
+ */
+hash_table_error_e hash_table_error(hash_table_p hash_table) {
+  hash_table_error_e error = hash_table->error;
+  hash_table->error = HT_NONE;
+
+  return error;
+}
+
+/**
+ * @brief Resize the internal element array of the hash table.
+ *
+ * Creates a new element array of the specified size and copies the existing
+ * elements into it. The original array is freed. If allocation fails,
+ * the error flag is set to HT_MEM.
+ *
+ * @param hash_table Pointer to the hash table.
+ * @param size       New size (number of slots) for the table.
+ */
+void hash_table_resize(hash_table_p hash_table, size_t size) {
+  hash_elem_t *new_array;
+
+  new_array = calloc(size, sizeof(hash_elem_t));
+  if (!new_array) {
+    hash_table->error = HT_MEM;
+    return;
+  }
+
+  memcpy(new_array, hash_table->elements,
+         hash_table->size * sizeof(hash_elem_t));
+
+  free(hash_table->elements);
+  hash_table->elements = new_array;
+}
+
+/**
+ * @brief Insert or update a key-value pair in the hash table.
+ *
+ * Computes a hash for the given key using CRC32 and attempts to place the
+ * value in the first available slot. If the key already exists, the error
+ * flag is set to HT_KEXIST and no insertion occurs. If the table is full,
+ * the error flag is set to HT_TEND. On success, the slot is marked as assigned.
+ *
+ * @param hash_table Pointer to the hash table.
+ * @param key        Null-terminated string key.
+ * @param value      Pointer to the value to store.
+ */
+void hash_table_set(hash_table_p hash_table, char *key, void *value) {
+  uint32_t crc = crc32((uint8_t *)key, strlen(key));
+
+  for (size_t i = 0; i < hash_table->size; i++) {
+    if (hash_table->elements[i].hash == crc) {
+      hash_table->error = HT_KEXIST;
+      return;
+    }
+
+    if (!hash_table->elements[i].is_assigned) {
+      hash_table->elements[i].hash = crc;
+      hash_table->elements[i].value = value;
+      hash_table->elements[i].is_assigned = true;
+      hash_table->error = HT_NONE;
+      return;
+    }
+  }
+
+  hash_table->error = HT_TEND;
+}
+
+/**
+ * @brief Retrieve a value by key from the hash table.
+ *
+ * Computes the hash for the key and searches linearly for a matching hash.
+ * If an empty slot is encountered before a match, the key is not present.
+ *
+ * @param hash_table Pointer to the hash table.
+ * @param key        Null-terminated string key.
+ * @return           Pointer to the stored value, or NULL if not found.
+ */
+void *hash_table_get(hash_table_p hash_table, char *key) {
+  uint32_t crc = crc32((uint8_t *)key, strlen(key));
+
+  for (size_t i = 0; i < hash_table->size; i++) {
+    if (!hash_table->elements[i].is_assigned) {
+      return NULL;
+    }
+
+    if (hash_table->elements[i].hash == crc) {
+      return hash_table->elements[i].value;
+    }
+  }
+
+  return NULL;
+}
+
+/**
+ * @brief Destroy the hash table and free all associated memory.
+ *
+ * Frees the internal element array and the table structure itself.
+ *
+ * @param hash_table Pointer to the hash table to deinitialize.
+ */
+void hash_table_deinit(hash_table_p hash_table) {
+  free(hash_table->elements);
+  free(hash_table);
+}

core/src/hash_table.h

@@ -0,0 +1,34 @@
+#ifndef HASH_TABLE_H
+#define HASH_TABLE_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+typedef enum {
+  HT_NONE = 0,
+  HT_TEND,   // End of table
+  HT_KEXIST, // Key exists
+  HT_MEM,    // Error while allocation
+} hash_table_error_e;
+
+typedef struct {
+  uint32_t hash;
+  void *value;
+  bool is_assigned;
+} hash_elem_t;
+
+typedef struct {
+  hash_elem_t *elements;
+  size_t size;
+  hash_table_error_e error;
+} hash_table_t, *hash_table_p;
+
+hash_table_p hash_table_init(size_t size);
+hash_table_error_e hash_table_error(hash_table_p hash_table);
+void hash_table_resize(hash_table_p hash_table, size_t size);
+void hash_table_set(hash_table_p hash_table, char *key, void *element);
+void *hash_table_get(hash_table_p hash_table, char *key);
+void hash_table_deinit(hash_table_p hash_table);
+
+#endif // !HASH_TABLE_H