no one knows what "special files" means

including two-days-ago me

include/aws/common/byte_buf.h

@@ -137,11 +137,11 @@ int aws_byte_buf_init_from_file(struct aws_byte_buf *out_buf, struct aws_allocat
 
 /**
  * Same as aws_byte_buf_init_from_file(), but for reading "special files" like /proc/cpuinfo.
- * This files don't accurately report their size, so size_hint is used as initial buffer size,
+ * These files don't accurately report their size, so size_hint is used as initial buffer size,
  * and the buffer grows until the while file is read.
  */
 AWS_COMMON_API
-int aws_byte_buf_init_from_special_file(
+int aws_byte_buf_init_from_file_with_size_hint(
     struct aws_byte_buf *out_buf,
     struct aws_allocator *alloc,
     const char *filename,

source/file.c

@@ -11,16 +11,15 @@
 
 #include <errno.h>
 
-/* For "special files", there's no point querying file size before reading.
+/* For "special files", the OS often lies about size.
  * For example, on Amazon Linux 2:
  * /proc/cpuinfo: size is 0, but contents are several KB of data.
  * /sys/devices/virtual/dmi/id/product_name: size is 4096, but contents are "c5.2xlarge"
  *
- * Therefore, let users pass a hint for the buffer's initial size,
- * and grow the buffer as necessary as we read until EOF.
+ * Therefore, we may need to grow the buffer as we read until EOF.
  * This is the min/max step size for growth. */
-#define MIN_BUFFER_GROWTH_READING_SPECIAL_FILES 32
-#define MAX_BUFFER_GROWTH_READING_SPECIAL_FILES 4096
+#define MIN_BUFFER_GROWTH_READING_FILES 32
+#define MAX_BUFFER_GROWTH_READING_FILES 4096
 
 FILE *aws_fopen(const char *file_path, const char *mode) {
     if (!file_path || strlen(file_path) == 0) {
@@ -90,8 +89,8 @@ static int s_byte_buf_init_from_file(
         /* Expand buffer if necessary (at a reasonable rate) */
         if (out_buf->len == out_buf->capacity) {
             size_t additional_capacity = out_buf->capacity;
-            additional_capacity = aws_max_size(MIN_BUFFER_GROWTH_READING_SPECIAL_FILES, additional_capacity);
-            additional_capacity = aws_min_size(MAX_BUFFER_GROWTH_READING_SPECIAL_FILES, additional_capacity);
+            additional_capacity = aws_max_size(MIN_BUFFER_GROWTH_READING_FILES, additional_capacity);
+            additional_capacity = aws_min_size(MAX_BUFFER_GROWTH_READING_FILES, additional_capacity);
             if (aws_byte_buf_reserve_relative(out_buf, additional_capacity)) {
                 AWS_LOGF_ERROR(AWS_LS_COMMON_IO, "static: Failed to grow buffer for file:'%s'", filename);
                 goto error;
@@ -146,7 +145,7 @@ int aws_byte_buf_init_from_file(struct aws_byte_buf *out_buf, struct aws_allocat
     return s_byte_buf_init_from_file(out_buf, alloc, filename, true /*use_file_size_as_hint*/, 0 /*size_hint*/);
 }
 
-int aws_byte_buf_init_from_special_file(
+int aws_byte_buf_init_from_file_with_size_hint(
     struct aws_byte_buf *out_buf,
     struct aws_allocator *alloc,
     const char *filename,

tests/file_test.c

@@ -462,29 +462,29 @@ static int s_create_file_then_read_it(struct aws_allocator *allocator, struct aw
     ASSERT_SUCCESS(s_check_byte_buf_from_file(&buf, contents));
     aws_byte_buf_clean_up(&buf);
 
-    /* now we check aws_byte_buf_init_from_special_file() with different size_hints */
+    /* now check aws_byte_buf_init_from_file_with_size_hint() ... */
 
     /* size_hint more then big enough */
     size_t size_hint = contents.len * 2;
-    ASSERT_SUCCESS(aws_byte_buf_init_from_special_file(&buf, allocator, filename, size_hint));
+    ASSERT_SUCCESS(aws_byte_buf_init_from_file_with_size_hint(&buf, allocator, filename, size_hint));
     ASSERT_SUCCESS(s_check_byte_buf_from_file(&buf, contents));
     aws_byte_buf_clean_up(&buf);
 
     /* size_hint not big enough for null-terminator */
     size_hint = contents.len;
-    ASSERT_SUCCESS(aws_byte_buf_init_from_special_file(&buf, allocator, filename, size_hint));
+    ASSERT_SUCCESS(aws_byte_buf_init_from_file_with_size_hint(&buf, allocator, filename, size_hint));
     ASSERT_SUCCESS(s_check_byte_buf_from_file(&buf, contents));
     aws_byte_buf_clean_up(&buf);
 
     /* size_hint 0 */
     size_hint = 0;
-    ASSERT_SUCCESS(aws_byte_buf_init_from_special_file(&buf, allocator, filename, size_hint));
+    ASSERT_SUCCESS(aws_byte_buf_init_from_file_with_size_hint(&buf, allocator, filename, size_hint));
     ASSERT_SUCCESS(s_check_byte_buf_from_file(&buf, contents));
     aws_byte_buf_clean_up(&buf);
 
     /* size_hint 1 */
     size_hint = 1;
-    ASSERT_SUCCESS(aws_byte_buf_init_from_special_file(&buf, allocator, filename, size_hint));
+    ASSERT_SUCCESS(aws_byte_buf_init_from_file_with_size_hint(&buf, allocator, filename, size_hint));
     ASSERT_SUCCESS(s_check_byte_buf_from_file(&buf, contents));
     aws_byte_buf_clean_up(&buf);
 
@@ -502,11 +502,13 @@ static int s_read_special_file(struct aws_allocator *allocator, const char *file
     }
 
     struct aws_byte_buf buf;
-    ASSERT_SUCCESS(aws_byte_buf_init_from_special_file(&buf, allocator, filename, 128));
+    ASSERT_SUCCESS(aws_byte_buf_init_from_file(&buf, allocator, filename));
     ASSERT_TRUE(buf.capacity > buf.len, "Buffer should end with null-terminator");
     ASSERT_UINT_EQUALS(0, buf.buffer[buf.len], "Buffer should end with null-terminator");
 
-    if (strcmp("/dev/null", filename) != 0) {
+    if (strcmp("/dev/null", filename) == 0) {
+        ASSERT_UINT_EQUALS(0, buf.len, "expected /dev/null to be empty");
+    } else {
         ASSERT_TRUE(buf.len > 0, "expected special file to have data");
     }
 
@@ -530,7 +532,7 @@ static int s_test_byte_buf_init_from_file(struct aws_allocator *allocator, void
     ASSERT_SUCCESS(s_create_file_then_read_it(allocator, aws_byte_cursor_from_buf(&big_rando)));
     aws_byte_buf_clean_up(&big_rando);
 
-    /* test aws_byte_buf_init_from_special_file() on actual "special files" (if they exist) */
+    /* test some "special files" (if they exist) */
     ASSERT_SUCCESS(s_read_special_file(allocator, "/proc/cpuinfo"));
     ASSERT_SUCCESS(s_read_special_file(allocator, "/proc/net/tcp"));
     ASSERT_SUCCESS(s_read_special_file(allocator, "/sys/devices/virtual/dmi/id/sys_vendor"));