feat(buffer): add buffer_slice util fn

include/libutil.h

@@ -177,10 +177,13 @@ void array_foreach(array_t *array, callback_t *callback);
  */
 array_t *array_concat(array_t *arr1, array_t *arr2);
 
+bool array_insert(array_t *array, unsigned int index, void *el,
+                  free_fn *free_old_el);
+
 /**
  * array_free frees the array and its internal state container. Safe to use
- * with an array of primitives. Accepts an optional function pointer if you want
- * all values to be freed.
+ * with an array of primitives. Accepts an optional function pointer if you
+ * want all values to be freed.
  */
 void array_free(array_t *array, free_fn *free_fnptr);
 
@@ -229,6 +232,18 @@ bool buffer_append_with(buffer_t *buf, const char *s, unsigned int len);
  */
 buffer_t *buffer_concat(buffer_t *buf_a, buffer_t *buf_b);
 
+/**
+ * Retrieve a slice of the buffer state.
+ *
+ * @param self the buffer instance
+ * @param start start index of the slice
+ * @param end_inclusive inclusive end index of the slice
+ * @param dest a buffer into which the slice will be stored
+ * @return int -1 if an error occurred, else 0
+ */
+int buffer_slice(buffer_t *self, unsigned int start, unsigned int end_inclusive,
+                 char *dest);
+
 /**
  * buffer_free deallocates the dynamic memory used by a given buffer_t*.
  */

src/array.c

@@ -112,6 +112,37 @@ bool array_push(array_t *array, void *el) {
   return true;
 }
 
+bool array_insert(array_t *array, unsigned int index, void *el,
+                  free_fn *free_old_el) {
+  __array_t *internal = (__array_t *)array;
+
+  if (internal->capacity < index) {
+    void **next_state = realloc(internal->state, (index) * sizeof(void *));
+    if (!next_state) {
+      free(next_state);
+      errno = ENOMEM;
+
+      return false;
+    }
+
+    internal->state = next_state;
+    internal->capacity = index;
+
+    internal->state[internal->size++] = el;
+
+    return true;
+  }
+
+  void *old_el = internal->state[internal->size++];
+  if (old_el && free_old_el) {
+    free_old_el(old_el);
+  }
+
+  internal->state[internal->size] = el;
+
+  return true;
+}
+
 void *array_pop(array_t *array) {
   __array_t *internal = (__array_t *)array;
 

src/buffer.c

@@ -91,3 +91,25 @@ void buffer_free(buffer_t *buf) {
 
   free(internal);
 }
+
+// TODO: error enums
+// TODO: rename all to `self`
+// TODO: remove inclusivity flags - user can just pass the end index they want
+int buffer_slice(buffer_t *self, unsigned int start, unsigned int end_inclusive,
+                 char *dest) {
+  __buffer_t *internal = (__buffer_t *)self;
+
+  if (internal->len < end_inclusive || internal->state == NULL) {
+    return -1;
+  }
+
+  unsigned int x = 0;
+  unsigned int i = start;
+  for (; i <= end_inclusive; i++, x++) {
+    memcpy(&dest[x], &internal->state[i], 1);
+  }
+
+  dest[x] = '\0';
+
+  return 0;
+}

t/array_test.c

@@ -325,11 +325,15 @@ void test_array_concat(void) {
   array_t *arr2 = array_collect(v[3], v[4], v[5]);
 
   array_t *concatenated = array_concat(arr1, arr2);
+  array_free(arr1, NULL);
+  array_free(arr2, NULL);
 
   ok(array_size(concatenated) == 6, "has the expected size");
   foreach (concatenated, i) {
     is(array_get(concatenated, i), v[i], "contains %s at index %d", v[i], i);
   }
+
+  array_free(concatenated, NULL);
 }
 
 void test_array_realloc_sanity(void) {
@@ -339,6 +343,7 @@ void test_array_realloc_sanity(void) {
   for (int i = 0; i < 20; i++) {
     array_push(arr, v);
   }
+  array_free(arr, NULL);
 }
 
 // bug fix
@@ -354,6 +359,15 @@ void test_array_get_negative_idx(void) {
   is(array_get(arr, -1), "y", "retrieves the new last element given index -1");
   is(array_get(arr, -2), "x",
      "retrieves the penultimate element given index -2");
+
+  array_free(arr, NULL);
+}
+
+void test_array_insert(void) {
+  array_t *arr = array_init();
+
+  array_insert(arr, 100, "xxx", NULL);
+  array_free(arr, NULL);
 }
 
 void run_array_tests(void) {

t/buffer_test.c

@@ -126,15 +126,61 @@ void test_buffer_free_nonnull(void) {
   lives({ buffer_free(buf); }, "frees the buffer's memory");
 }
 
+void test_buffer_slice_ok(void) {
+  buffer_t *buf = buffer_init("test world test");
+
+  char slice[32];
+  int ret = buffer_slice(buf, 5, 9, slice);
+  ok(ret == 0, "retval is zero indicating no errors");
+  is(slice, "world", "returns the expected slice");
+}
+
+void test_buffer_slice_empty_buffer(void) {
+  buffer_t *buf = buffer_init("");
+
+  char slice[32];
+  int ret = buffer_slice(buf, 0, 0, slice);
+  ok(ret == 0, "retval is zero indicating no errors");
+  is(slice, "", "returns the expected slice");
+}
+
+void test_buffer_slice_bad_range(void) {
+  buffer_t *buf = buffer_init("test world test");
+
+  char slice[32];
+  int ret = buffer_slice(
+      buf, 5, 32,
+      NULL);  // No segfault from this proves the function fast-fails
+  ok(ret == -1, "retval is -1 indicating a bad range");
+}
+
+void test_buffer_slice_null_buffer(void) {
+  buffer_t *buf = buffer_init(NULL);
+
+  char slice[32];
+  int ret = buffer_slice(buf, 0, 0, NULL);
+  ok(ret == -1, "retval is -1 indicating a NULL internal state");
+}
+
 void run_buffer_tests(void) {
+  test_buffer_init();
+  test_buffer_init_with_initial();
+
   test_buffer_free();
   test_buffer_free_nonnull();
-  test_buffer_init();
+
   test_buffer_size();
+
   test_buffer_state();
-  test_buffer_init_with_initial();
+
   test_buffer_append();
   test_buffer_append_with();
+
   test_buffer_concat();
   test_buffer_concat_on_null();
+
+  test_buffer_slice_ok();
+  test_buffer_slice_empty_buffer();
+  test_buffer_slice_bad_range();
+  test_buffer_slice_null_buffer();
 }

t/io_test.c

@@ -18,8 +18,8 @@ void test_read_all_full_file() {
   size_t sz = sizeof(data);
   read_all_result ret = read_all(fd, &data, &sz);
 
-  ok(READ_ALL_OK == ret, "returns READ_ALL_OK on successful read\n");
-  ok(sz == 68241, "reads the correct number of bytes\n");
+  ok(READ_ALL_OK == ret, "returns READ_ALL_OK on successful read");
+  ok(sz == 68241, "reads the correct number of bytes");
   is("The Colour Out of Space\n", s_substr(data, 0, 23, true),
      "first chars match");
   is("troubling my sleep.\n", s_substr(data, 68221, 68241, true),

t/main.c

@@ -2,7 +2,7 @@
 #include "tests.h"
 
 int main() {
-  plan(171);
+  plan(177);
 
   run_array_tests();
   run_buffer_tests();