I recently picked up C, because I am getting tired of the hell that is Java Enterprise development. I decided that writing a Huffman compressor will be a great little exercise, and I have always wanted to write a compression algorithm. I want some pointers(get it) on how to make the code more idiomatic, modular and less verbose.
#include <stdio.h> #include <stdlib.h> #include <string.h> #define MAX_SZ 128 #define MAX_CODE_LEN 64 int counts[MAX_SZ]; char codes[MAX_SZ][MAX_CODE_LEN]; typedef struct Node { char character; int count; struct Node *left; struct Node *right; } Node; void calculate_prob(char *str, int *counts) { int len = strlen(str); for (int i = 0; i < len; i++) { counts[*str++]++; } } int comparator(const void *a, const void *b) { Node *n1 = (Node *)a; Node *n2 = (Node *)b; return (n1->count - n2->count); } Node *find_and_remove_min(Node *nodes, int sz) { int idx = 0; Node *minNode = &nodes[0]; for (int i = 0; i < sz; i++) { if (nodes[i].count < minNode->count) { minNode = &nodes[i]; idx = i; } } Node *node = (Node *)malloc(sizeof(Node)); memcpy(node, minNode, sizeof(Node)); nodes[idx] = nodes[sz - 1]; return node; } void dfs(Node *node, char *path, int sz) { if (node == NULL) { return; } if (node->left == NULL && node->right == NULL) { strncpy(codes[node->character], path, sz); return; } path[sz] = '0'; dfs(node->left, path, sz + 1); path[sz] = '1'; dfs(node->right, path, sz + 1); } char *fileToString(char *file_name) { FILE *file = fopen(file_name, "r"); if (file == NULL) return NULL; fseek(file, 0, SEEK_END); long int size = ftell(file); fclose(file); file = fopen(file_name, "r"); char *str = (char *)malloc(size); int bytes_read = fread(str, sizeof(char), size, file); fclose(file); return str; } void writeCodeBook(FILE* file){ for (int i = 0; i < MAX_SZ; i++) { if (codes[i][0] == '\0') { continue; } putc((char)i, file); putc(':', file); fwrite(codes[i], sizeof(char), strlen(codes[i]), file); putc('\n', file); } } void writeBitToFile(unsigned char bit, FILE *file, int flush) { static int count = 0; static char buffer = 0; if(flush){ buffer <<= (8 - count); fwrite(&buffer, sizeof(buffer), 1, file); return; } buffer <<= 1; // Make room for next bit. if (bit) buffer |= 1; // Set if necessary. count++; if (count == 8) { fwrite(&buffer, sizeof(buffer), 1, file); // Error handling elided. buffer = 0; count = 0; } } int main(int argc, char **argv) { char *str = NULL; if (argc > 1) { str = fileToString(argv[1]); } else { return 1; } calculate_prob(str, counts); int node_count = 0; for (int i = 0; i < MAX_SZ; i++) { if (counts[i] != 0) { node_count++; } } const int SZ = node_count; Node nodes[SZ]; for (int i = 0, idx = 0; i < MAX_SZ; i++) { if (counts[i] != 0) { struct Node node = {(char)i, counts[i], NULL, NULL}; nodes[idx++] = node; } } qsort(nodes, SZ, sizeof(Node), comparator); int sz = SZ; Node *root = NULL; while (sz != 1) { struct Node *min = find_and_remove_min(nodes, sz); struct Node *min_2 = NULL; sz--; min_2 = find_and_remove_min(nodes, sz); Node new_node = {'\0', min->count + min_2->count, min, min_2}; nodes[sz - 1] = new_node; root = &new_node; } char path[MAX_CODE_LEN]; memset(path, '\0', MAX_CODE_LEN); dfs(root, path, 0); FILE *file = NULL; if (argc > 2) { file = fopen(argv[2], "w+"); } else { return 1; } writeCodeBook(file); for (char *s = str; *s; s++) { char *code = codes[*s]; int len = strlen(code); for (int i = 0; i < len; i++) { unsigned char bit = code[i] - '0'; // printf("%d", bit); writeBitToFile(bit, file, 0); } } writeBitToFile(0, file, 1); } ``` 
