14 files changed, 939 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..8ecde1b
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+build/
+bf.out
+compile_commands.json
+test.bf
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..8c7470c
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,26 @@
+CFLAGS := -Isrc -MMD -MP -Wall -Wextra
+LDFLAGS := 
+
+TARGET = build/bfc
+
+TARGET_SRC := $(shell find src -name "*.c")
+TARGET_OBJ := $(patsubst src/%.c, build/%.o, $(TARGET_SRC))
+TARGET_DEP := $(patsubst build/%.o, build/%.d, $(TARGET_OBJ))
+
+all: build $(TARGET)
+
+build:
+	mkdir -p $(sort $(dir $(TARGET_OBJ)))
+
+$(TARGET): $(TARGET_OBJ)
+	$(CC) $(LDFLAGS) $(TARGET_OBJ) -o $@
+
+-include $(TARGET_DEP)
+
+build/%.o: src/%.c
+	$(CC) $(CFLAGS) -c $< -o $@
+
+clean:
+	rm -rf build
+
+.PHONY: build clean
diff --git a/bfc.sh b/bfc.sh
new file mode 100755
index 0000000..4bc87c1
--- /dev/null
+++ b/bfc.sh
@@ -0,0 +1,24 @@
+#!/usr/bin/env sh
+
+set -e
+
+BFC="./build/bfc"
+SRC="$1"
+
+if [ -z "$SRC" ]; then
+  echo "usage: $0 <file.bf>" >&2
+  exit 1
+fi
+
+# silently build compiler if missing
+if [ ! -f "$BFC" ]; then
+  make -s || {
+    echo "build failed" >&2
+    exit 1
+  }
+fi
+
+# compile pipeline
+OUT=$(cat "$SRC" | "$BFC")
+
+echo "$OUT" | gcc -o ./bf.out -x c -
diff --git a/src/all.h b/src/all.h
new file mode 100644
index 0000000..c5a983c
--- /dev/null
+++ b/src/all.h
@@ -0,0 +1,65 @@
+#pragma once
+#include "ivec.h"
+#include "node_vec.h"
+#include "str.h"
+#include <stdbool.h>
+#include <stddef.h>
+
+// Lexer
+
+typedef enum {
+  LEX_PINC,
+  LEX_PDEC,
+  LEX_VINC,
+  LEX_VDEC,
+  LEX_OUT,
+  LEX_IN,
+  LEX_LB,
+  LEX_RB,
+  LEX_EOF
+} lex_tok_e;
+
+typedef struct {
+  str *src;
+  size_t pos;
+  ivec tokens;
+} lexer_t;
+
+lexer_t lex_init(str *src);
+void lex_run(lexer_t *lx);
+void lex_free(lexer_t *lx);
+
+// Parser/AST
+
+typedef struct ast_node ast_node_t;
+
+typedef enum {
+  AST_INC,
+  AST_DEC,
+  AST_PTR_INC,
+  AST_PTR_DEC,
+  AST_OUT,
+  AST_IN,
+  AST_LOOP
+} ast_type_e;
+
+struct ast_node {
+  ast_type_e type;
+  int val;
+
+  node_vec children; // vec<ast_node_t*>
+  ast_node_t *next;
+};
+
+typedef struct {
+  lexer_t *lx;
+  size_t pos;
+} parser_t;
+
+parser_t parser_init(lexer_t *lx);
+ast_node_t *parse_program(parser_t *p);
+void ast_free(ast_node_t *node);
+
+// codegen
+
+str gen_code(ast_node_t *ast);
diff --git a/src/bfc.c b/src/bfc.c
new file mode 100644
index 0000000..2e369cf
--- /dev/null
+++ b/src/bfc.c
@@ -0,0 +1,30 @@
+#include "all.h"
+#include "str.h"
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+int main(void) {
+  str input = {0};
+  str_append_fread(&input, stdin);
+
+  lexer_t lexer = lex_init(&input);
+  lex_run(&lexer);
+
+  parser_t p = parser_init(&lexer);
+
+  ast_node_t *ast = parse_program(&p);
+
+  // lex_free(&lexer);
+  // parser_free(&p);
+
+  str c_code = gen_code(ast);
+
+  ast_free(ast);
+
+  printf("%s", c_code.data);
+
+  free_str(&input);
+  return 0;
+}
diff --git a/src/codegen.c b/src/codegen.c
new file mode 100644
index 0000000..e4972db
--- /dev/null
+++ b/src/codegen.c
@@ -0,0 +1,148 @@
+#include "all.h"
+#include "str.h"
+
+static void emit_includes(str *out) {
+  str_append(out, "#include <stdio.h>\n");
+  str_append(out, "#include <stdlib.h>\n");
+  str_append(out, "#include <string.h>\n\n");
+}
+
+static void emit_runtime(str *out) {
+  str_append(
+      out,
+      "typedef struct {\n"
+      "    unsigned char *data;\n"
+      "    size_t size;\n"
+      "} tape_t;\n\n"
+
+      "static void tape_init(tape_t *t, size_t initial) {\n"
+      "    t->data = calloc(initial, 1);\n"
+      "    t->size = initial;\n"
+      "}\n\n"
+
+      "static void tape_grow_right(tape_t *t, size_t needed) {\n"
+      "    size_t new_size = t->size;\n"
+      "    while (new_size <= needed) new_size *= 2;\n"
+      "    unsigned char *new_data = calloc(new_size, 1);\n"
+      "    memcpy(new_data, t->data, t->size);\n"
+      "    free(t->data);\n"
+      "    t->data = new_data;\n"
+      "    t->size = new_size;\n"
+      "}\n\n"
+
+      "static void tape_grow_left(tape_t *t, size_t add, size_t *ptr) {\n"
+      "    size_t new_size = t->size + add;\n"
+      "    unsigned char *new_data = calloc(new_size, 1);\n"
+      "    memcpy(new_data + add, t->data, t->size);\n"
+      "    free(t->data);\n"
+      "    t->data = new_data;\n"
+      "    t->size = new_size;\n"
+      "    *ptr += add;\n"
+      "}\n\n"
+
+      "static void tape_move_right(tape_t *t, size_t *ptr, size_t amount) {\n"
+      "    *ptr += amount;\n"
+      "    if (*ptr >= t->size)\n"
+      "        tape_grow_right(t, *ptr);\n"
+      "}\n\n"
+
+      "static void tape_move_left(tape_t *t, size_t *ptr, size_t amount) {\n"
+      "    if (amount > *ptr) {\n"
+      "        size_t need = amount - *ptr;\n"
+      "        size_t add = t->size;\n"
+      "        while (add <= need)\n"
+      "            add *= 2;\n"
+      "        tape_grow_left(t, add, ptr);\n"
+      "    }\n"
+      "    *ptr -= amount;\n"
+      "}\n\n");
+}
+
+static void emit_prelude(str *out) {
+  str_append(out, "int main(void)\n"
+                  "{\n"
+                  "    tape_t tape;\n"
+                  "    tape_init(&tape, 32);\n"
+                  "    size_t ptr = tape.size / 2;\n\n");
+}
+
+static void emit_epilogue(str *out) {
+  str_append(out, "    free(tape.data);\n"
+                  "    return 0;\n"
+                  "}\n");
+}
+
+static void emit_indent(str *out, int indent) {
+  for (int i = 0; i < indent; i++)
+    str_append(out, "    ");
+}
+
+void emit_node(str *out, ast_node_t *node, int indent) {
+  for (; node; node = node->next) {
+    switch (node->type) {
+    case AST_INC:
+      emit_indent(out, indent);
+      str_append(out, "tape.data[ptr] += ");
+      str_appendf(out, "%d;\n", node->val);
+      break;
+
+    case AST_DEC:
+      emit_indent(out, indent);
+      str_append(out, "tape.data[ptr] -= ");
+      str_appendf(out, "%d;\n", node->val);
+      break;
+
+    case AST_PTR_INC:
+      emit_indent(out, indent);
+      str_append(out, "tape_move_right(&tape, &ptr, ");
+      str_appendf(out, "%d", node->val);
+      str_append(out, ");\n");
+      break;
+
+    case AST_PTR_DEC:
+      emit_indent(out, indent);
+      str_append(out, "tape_move_left(&tape, &ptr, ");
+      str_appendf(out, "%d", node->val);
+      str_append(out, ");\n");
+      break;
+
+    case AST_OUT:
+      emit_indent(out, indent);
+      str_append(out, "putchar((int)tape.data[ptr]);\n");
+      break;
+
+    case AST_IN:
+      emit_indent(out, indent);
+      str_append(out,
+                 "{ int ch = getchar();\n"
+                 "  tape.data[ptr] = (ch == EOF) ? 0 : (unsigned char)ch; }\n");
+      break;
+
+    case AST_LOOP:
+      emit_indent(out, indent);
+      str_append(out, "while (tape.data[ptr]) {\n");
+
+      for (int i = 0; i < node->children.len; i++) {
+        emit_node(out, node->children._data[i], indent + 1);
+      }
+
+      emit_indent(out, indent);
+      str_append(out, "}\n");
+      break;
+    }
+  }
+}
+
+str gen_code(ast_node_t *ast) {
+  str out = {0};
+
+  emit_includes(&out);
+  emit_runtime(&out);
+  emit_prelude(&out);
+
+  emit_node(&out, ast, 1);
+
+  emit_epilogue(&out);
+
+  return out;
+}
diff --git a/src/ivec.c b/src/ivec.c
new file mode 100644
index 0000000..9c0dd95
--- /dev/null
+++ b/src/ivec.c
@@ -0,0 +1,119 @@
+#include "ivec.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+void iv_free(ivec *v) {
+  free(v->_data);
+  v->_data = NULL;
+  v->_cap = 0;
+  v->len = 0;
+}
+
+static void _iv_ensure_init(ivec *v) {
+  if (v->_data)
+    return;
+
+  v->_cap = 16;
+  v->len = 0;
+
+  v->_data = malloc(v->_cap * sizeof(long long));
+  if (!v->_data) {
+    perror("_v_ensure_init.malloc");
+    abort();
+  }
+}
+
+static void _iv_ensure_capacity(ivec *v) {
+  _iv_ensure_init(v);
+
+  if (v->len >= v->_cap) {
+    v->_cap = (v->_cap == 0) ? 16 : v->_cap * 2;
+
+    long long *tmp = realloc(v->_data, v->_cap * sizeof(long long));
+    if (!tmp) {
+      perror("_v_ensure_capacity.realloc");
+      abort();
+    }
+
+    v->_data = tmp;
+  }
+}
+
+size_t iv_push(ivec *v, long long data) {
+  _iv_ensure_capacity(v);
+
+  v->_data[v->len++] = data;
+  return v->len - 1;
+}
+
+// getter
+long long iv_get(ivec *v, size_t idx) {
+  _iv_ensure_init(v);
+
+  if (idx < v->len) {
+    return v->_data[idx];
+  }
+
+  return 0;
+}
+
+// O(n) shift delete
+long long iv_rem_shift(ivec *v, size_t idx) {
+  _iv_ensure_init(v);
+
+  if (idx >= v->len)
+    return 0;
+
+  int old = v->_data[idx];
+
+  for (size_t j = idx; j + 1 < v->len; j++) {
+    v->_data[j] = v->_data[j + 1];
+  }
+
+  v->len--;
+  return old;
+}
+
+// O(1) swap delete
+long long iv_rem(ivec *v, size_t idx) {
+  _iv_ensure_init(v);
+
+  if (idx >= v->len)
+    return 0;
+
+  int old = v->_data[idx];
+  v->_data[idx] = v->_data[--v->len];
+  return old;
+}
+
+// search
+long long iv_has(ivec *v, long long x,
+                 int (*comp)(const long long, const long long)) {
+  _iv_ensure_init(v);
+
+  if (!comp)
+    return 0;
+
+  for (size_t i = 0; i < v->len; i++) {
+    if (comp(v->_data[i], x) == 0) {
+      return v->_data[i];
+    }
+  }
+
+  return 0;
+}
+
+void iv_shrink(ivec *v) {
+  _iv_ensure_init(v);
+
+  size_t new_cap = v->len ? v->len : 1;
+
+  long long *tmp = realloc(v->_data, new_cap * sizeof(int)); // FIX
+  if (!tmp) {
+    perror("v_shrink.realloc");
+    abort();
+  }
+
+  v->_cap = new_cap;
+  v->_data = tmp;
+}
diff --git a/src/ivec.h b/src/ivec.h
new file mode 100644
index 0000000..8526171
--- /dev/null
+++ b/src/ivec.h
@@ -0,0 +1,18 @@
+#pragma once
+
+#include <stddef.h>
+
+typedef struct {
+  long long *_data;
+  size_t _cap;
+  size_t len;
+} ivec;
+
+void iv_free(ivec *v);
+size_t iv_push(ivec *v, long long data);
+long long iv_get(ivec *v, size_t idx);
+long long iv_rem_shift(ivec *v, size_t idx);
+long long iv_rem(ivec *v, size_t idx);
+long long iv_has(ivec *v, long long x,
+                 int (*comp)(const long long, const long long));
+void iv_shrink(ivec *v);
diff --git a/src/lexer.c b/src/lexer.c
new file mode 100644
index 0000000..4f1fcd0
--- /dev/null
+++ b/src/lexer.c
@@ -0,0 +1,72 @@
+#include "all.h"
+#include "ivec.h"
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+lexer_t lex_init(str *src) {
+  lexer_t lx = {0};
+
+  lx.src = src;
+  lx.pos = 0;
+  lx.tokens = (ivec){0};
+
+  return lx;
+}
+
+void lex_run(lexer_t *lx) {
+  for (size_t i = 0; i < lx->src->length; i++) {
+
+    char c = lx->src->data[i];
+    lex_tok_e tok;
+
+    switch (c) {
+    case '+':
+      tok = LEX_PINC;
+      break;
+    case '-':
+      tok = LEX_PDEC;
+      break;
+    case '>':
+      tok = LEX_VINC;
+      break;
+    case '<':
+      tok = LEX_VDEC;
+      break;
+    case '.':
+      tok = LEX_OUT;
+      break;
+    case ',':
+      tok = LEX_IN;
+      break;
+    case '[':
+      tok = LEX_LB;
+      break;
+    case ']':
+      tok = LEX_RB;
+      break;
+    default:
+      continue;
+    }
+
+    iv_push(&lx->tokens, tok);
+  }
+
+  iv_push(&lx->tokens, LEX_EOF);
+}
+
+void lex_free(lexer_t *lx) {
+  if (!lx)
+    return;
+
+  iv_free(&lx->tokens);
+
+  if (lx->src) {
+    free(lx->src->data);
+    free(lx->src);
+  }
+
+  lx->src = NULL;
+  lx->pos = 0;
+}
diff --git a/src/node_vec.c b/src/node_vec.c
new file mode 100644
index 0000000..f327585
--- /dev/null
+++ b/src/node_vec.c
@@ -0,0 +1,114 @@
+#include "node_vec.h"
+#include "all.h"
+#include <stdio.h>
+#include <stdlib.h>
+
+void node_vec_free(node_vec *v) {
+  free(v->_data);
+  v->_data = NULL;
+  v->_cap = 0;
+  v->len = 0;
+}
+
+static void _node_vec_init(node_vec *v) {
+  if (v->_data)
+    return;
+
+  v->_cap = 16;
+  v->len = 0;
+
+  v->_data = malloc(v->_cap * sizeof(ast_node_t *));
+  if (!v->_data) {
+    perror("_node_vec_init.malloc");
+    abort();
+  }
+}
+
+static void _node_vec_ensure(node_vec *v) {
+  _node_vec_init(v);
+
+  if (v->len >= v->_cap) {
+    v->_cap = (v->_cap == 0) ? 16 : v->_cap * 2;
+
+    ast_node_t **tmp = realloc(v->_data, v->_cap * sizeof(ast_node_t *));
+    if (!tmp) {
+      perror("_node_vec_ensure.realloc");
+      abort();
+    }
+
+    v->_data = tmp;
+  }
+}
+
+size_t node_vec_push(node_vec *v, ast_node_t *data) {
+  _node_vec_ensure(v);
+
+  v->_data[v->len++] = data;
+  return v->len - 1;
+}
+
+ast_node_t *node_vec_get(node_vec *v, size_t idx) {
+  _node_vec_init(v);
+
+  if (idx < v->len)
+    return v->_data[idx];
+
+  return NULL;
+}
+
+ast_node_t *node_vec_rem_shift(node_vec *v, size_t idx) {
+  _node_vec_init(v);
+
+  if (idx >= v->len)
+    return NULL;
+
+  ast_node_t *old = v->_data[idx];
+
+  for (size_t j = idx; j + 1 < v->len; j++) {
+    v->_data[j] = v->_data[j + 1];
+  }
+
+  v->len--;
+  return old;
+}
+
+ast_node_t *node_vec_rem(node_vec *v, size_t idx) {
+  _node_vec_init(v);
+
+  if (idx >= v->len)
+    return NULL;
+
+  ast_node_t *old = v->_data[idx];
+  v->_data[idx] = v->_data[--v->len];
+  return old;
+}
+
+ast_node_t *node_vec_has(node_vec *v, ast_node_t *x,
+                         int (*comp)(const ast_node_t *, const ast_node_t *)) {
+  _node_vec_init(v);
+
+  if (!comp)
+    return NULL;
+
+  for (size_t i = 0; i < v->len; i++) {
+    if (comp(v->_data[i], x) == 0)
+      return v->_data[i];
+  }
+
+  return NULL;
+}
+
+void node_vec_shrink(node_vec *v) {
+  _node_vec_init(v);
+
+  size_t new_cap = v->len ? v->len : 1;
+
+  ast_node_t **tmp = realloc(v->_data, new_cap * sizeof(ast_node_t *));
+  if (!tmp) {
+    perror("node_vec_shrink.realloc");
+    abort();
+  }
+
+  v->_cap = new_cap;
+  v->_data = tmp;
+}
diff --git a/src/node_vec.h b/src/node_vec.h
new file mode 100644
index 0000000..8421d32
--- /dev/null
+++ b/src/node_vec.h
@@ -0,0 +1,26 @@
+#pragma once
+
+#include <stddef.h>
+
+typedef struct ast_node ast_node_t;
+
+typedef struct {
+  ast_node_t **_data;
+  size_t _cap;
+  size_t len;
+} node_vec;
+
+void node_vec_free(node_vec *v);
+
+size_t node_vec_push(node_vec *v, ast_node_t *data);
+
+ast_node_t *node_vec_get(node_vec *v, size_t idx);
+
+ast_node_t *node_vec_rem_shift(node_vec *v, size_t idx);
+
+ast_node_t *node_vec_rem(node_vec *v, size_t idx);
+
+ast_node_t *node_vec_has(node_vec *v, ast_node_t *x,
+                         int (*comp)(const ast_node_t *, const ast_node_t *));
+
+void node_vec_shrink(node_vec *v);
diff --git a/src/parser.c b/src/parser.c
new file mode 100644
index 0000000..855b94e
--- /dev/null
+++ b/src/parser.c
@@ -0,0 +1,152 @@
+#include "all.h"
+#include "ivec.h"
+#include "node_vec.h"
+#include <stdint.h>
+#include <stdlib.h>
+
+static inline lex_tok_e peek(parser_t *p) {
+  return iv_get(&p->lx->tokens, p->pos);
+}
+
+static inline lex_tok_e advance(parser_t *p) {
+  return iv_get(&p->lx->tokens, p->pos++);
+}
+
+static ast_node_t *new_node(ast_type_e type, int val) {
+  ast_node_t *n = malloc(sizeof(ast_node_t));
+  n->type = type;
+  n->val = val;
+  n->next = NULL;
+  n->children = (node_vec){0};
+  return n;
+}
+
+static ast_node_t *parse_block(parser_t *p);
+
+static ast_node_t *parse_single(parser_t *p) {
+  lex_tok_e t = peek(p);
+
+  switch (t) {
+
+  case LEX_PINC: {
+    int count = 0;
+    while (peek(p) == LEX_PINC) {
+      advance(p);
+      count++;
+    }
+    return new_node(AST_INC, count);
+  }
+
+  case LEX_PDEC: {
+    int count = 0;
+    while (peek(p) == LEX_PDEC) {
+      advance(p);
+      count++;
+    }
+    return new_node(AST_DEC, count);
+  }
+
+  case LEX_VINC: {
+    int count = 0;
+    while (peek(p) == LEX_VINC) {
+      advance(p);
+      count++;
+    }
+    return new_node(AST_PTR_INC, count);
+  }
+
+  case LEX_VDEC: {
+    int count = 0;
+    while (peek(p) == LEX_VDEC) {
+      advance(p);
+      count++;
+    }
+    return new_node(AST_PTR_DEC, count);
+  }
+
+  case LEX_OUT:
+    advance(p);
+    return new_node(AST_OUT, 1);
+
+  case LEX_IN:
+    advance(p);
+    return new_node(AST_IN, 1);
+
+  case LEX_LB:
+    advance(p); // consume '['
+    return parse_block(p);
+
+  case LEX_RB:
+    return NULL;
+
+  case LEX_EOF:
+    return NULL;
+
+  default:
+    advance(p);
+    return NULL;
+  }
+}
+
+static ast_node_t *parse_block(parser_t *p) {
+  ast_node_t *loop = new_node(AST_LOOP, 1);
+
+  while (1) {
+    lex_tok_e t = peek(p);
+
+    if (t == LEX_EOF) {
+      break;
+    }
+
+    if (t == LEX_RB) {
+      advance(p); // consume ']'
+      break;
+    }
+
+    ast_node_t *child = parse_single(p);
+    if (child) {
+      node_vec_push(&loop->children, child);
+    }
+  }
+
+  return loop;
+}
+
+parser_t parser_init(lexer_t *lx) { return (parser_t){.lx = lx, .pos = 0}; }
+
+ast_node_t *parse_program(parser_t *p) {
+  ast_node_t *head = NULL;
+  ast_node_t *tail = NULL;
+
+  while (peek(p) != LEX_EOF) {
+
+    ast_node_t *node = parse_single(p);
+    if (!node)
+      continue;
+
+    if (!head) {
+      head = tail = node;
+    } else {
+      tail->next = node;
+      tail = node;
+    }
+  }
+
+  return head;
+}
+
+void ast_free(ast_node_t *node) {
+  if (!node)
+    return;
+
+  if (node->next)
+    ast_free(node->next);
+
+  for (size_t i = 0; i < node->children.len; i++) {
+    ast_free(node->children._data[i]);
+  }
+
+  node_vec_free(&node->children);
+
+  free(node);
+}
diff --git a/src/str.c b/src/str.c
new file mode 100644
index 0000000..ddca742
--- /dev/null
+++ b/src/str.c
@@ -0,0 +1,119 @@
+#include "str.h"
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define STARTING_SIZE 256
+#define READ_CHUNK_SIZE 1024
+
+static void str_ensure_init(str *s) {
+  if (s->data)
+    return;
+
+  s->capacity = STARTING_SIZE;
+  s->length = 0;
+  s->data = malloc(s->capacity);
+  if (!s->data)
+    abort();
+
+  s->data[0] = '\0';
+}
+
+static void str_ensure_capacity(str *s, size_t extra) {
+  str_ensure_init(s);
+
+  size_t needed = s->length + extra + 1; // +1 for '\0'
+  if (needed <= s->capacity)
+    return;
+
+  while (s->capacity < needed)
+    s->capacity *= 2;
+
+  char *new_data = realloc(s->data, s->capacity);
+  if (!new_data)
+    abort();
+
+  s->data = new_data;
+}
+
+void free_str(str *s) {
+  free(s->data);
+  s->data = NULL;
+  s->length = 0;
+  s->capacity = 0;
+}
+
+void str_append(str *s, const char *from) {
+  str_append_len(s, from, strlen(from));
+}
+
+void str_append_c(str *s, char c) { str_append_len(s, &c, 1); }
+
+void str_append_len(str *s, const char *from, size_t len) {
+  str_ensure_capacity(s, len);
+
+  memcpy(s->data + s->length, from, len);
+  s->length += len;
+  s->data[s->length] = '\0';
+}
+
+void str_append_read(str *s, int fd) {
+  char buf[READ_CHUNK_SIZE];
+  ssize_t n;
+
+  while ((n = read(fd, buf, sizeof(buf))) > 0) {
+    str_append_len(s, buf, (size_t)n);
+  }
+}
+
+void str_append_fread(str *s, FILE *file) {
+  char buf[READ_CHUNK_SIZE];
+  size_t n;
+
+  while ((n = fread(buf, 1, sizeof(buf), file)) > 0) {
+    str_append_len(s, buf, n);
+  }
+}
+
+void str_append_fread_len(str *s, size_t size, FILE *file) {
+  char buf[READ_CHUNK_SIZE];
+
+  while (size > 0) {
+    size_t chunk = size > sizeof(buf) ? sizeof(buf) : size;
+    size_t n = fread(buf, 1, chunk, file);
+
+    if (n == 0)
+      break;
+
+    str_append_len(s, buf, n);
+    size -= n;
+
+    if (n < chunk)
+      break;
+  }
+}
+
+void str_appendf(str *s, const char *fmt, ...) {
+  va_list args;
+  va_start(args, fmt);
+
+  va_list copy;
+  va_copy(copy, args);
+  int needed = vsnprintf(NULL, 0, fmt, copy);
+  va_end(copy);
+
+  if (needed < 0) {
+    va_end(args);
+    return;
+  }
+
+  str_ensure_capacity(s, (size_t)needed);
+
+  vsnprintf(s->data + s->length, s->capacity - s->length, fmt, args);
+  s->length += (size_t)needed;
+
+  va_end(args);
+}
diff --git a/src/str.h b/src/str.h
new file mode 100644
index 0000000..416a846
--- /dev/null
+++ b/src/str.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdio.h>
+
+typedef struct {
+  char *data;
+  size_t length;
+  size_t capacity;
+} str;
+
+void free_str(str *s);
+
+void str_append(str *s, const char *from);
+void str_append_c(str *s, char c);
+void str_append_len(str *s, const char *from, size_t len);
+
+void str_append_read(str *s, int fd);
+void str_append_fread(str *s, FILE *file);
+void str_append_fread_len(str *s, size_t size, FILE *file);
+
+void str_appendf(str *s, const char *fmt, ...);