chore: Clean up the return statements and update example.c accordingly

Author: ctruta

example.c

@@ -3,7 +3,7 @@
 
 /* example.c - an example of using libpng
  *
- * Maintained 2018 Cosmin Truta
+ * Maintained 2018-2024 Cosmin Truta
  * Maintained 1998-2016 Glenn Randers-Pehrson
  * Maintained 1996-1997 Andreas Dilger
  * Written 1995-1996 Guy Eric Schalnat, Group 42, Inc.
@@ -259,9 +259,9 @@ int check_if_png(char *file_name, FILE **fp)
       return 0;
 
    /* Compare the first PNG_BYTES_TO_CHECK bytes of the signature.
-    * Return nonzero (true) if they match.
+    * Return true if they match.
     */
-   return(!png_sig_cmp(buf, 0, PNG_BYTES_TO_CHECK));
+   return png_sig_cmp(buf, 0, PNG_BYTES_TO_CHECK) == 0;
 }
 
 /* Read a PNG file.  You may want to return an error code if the read
@@ -281,7 +281,7 @@ void read_png(char *file_name) /* We need to open the file */
    FILE *fp;
 
    if ((fp = fopen(file_name, "rb")) == NULL)
-      return (ERROR);
+      return ERROR;
 
 #else no_open_file /* prototype 2 */
 void read_png(FILE *fp, int sig_read) /* File is already open */
@@ -304,7 +304,7 @@ void read_png(FILE *fp, int sig_read) /* File is already open */
    if (png_ptr == NULL)
    {
       fclose(fp);
-      return (ERROR);
+      return ERROR;
    }
 
    /* Allocate/initialize the memory for image information.  REQUIRED. */
@@ -313,7 +313,7 @@ void read_png(FILE *fp, int sig_read) /* File is already open */
    {
       fclose(fp);
       png_destroy_read_struct(&png_ptr, NULL, NULL);
-      return (ERROR);
+      return ERROR;
    }
 
    /* Set error handling if you are using the setjmp/longjmp method (this is
@@ -326,7 +326,7 @@ void read_png(FILE *fp, int sig_read) /* File is already open */
       png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
       fclose(fp);
       /* If we get here, we had a problem reading the file. */
-      return (ERROR);
+      return ERROR;
    }
 
    /* One of the following I/O initialization methods is REQUIRED. */
@@ -585,7 +585,7 @@ void read_png(FILE *fp, int sig_read) /* File is already open */
    fclose(fp);
 
    /* That's it! */
-   return (OK);
+   return OK;
 }
 
 /* Progressively read a file */
@@ -604,18 +604,18 @@ initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr)
    if (*png_ptr == NULL)
    {
       *info_ptr = NULL;
-      return (ERROR);
+      return ERROR;
    }
    *info_ptr = png_create_info_struct(png_ptr);
    if (*info_ptr == NULL)
    {
       png_destroy_read_struct(png_ptr, info_ptr, NULL);
-      return (ERROR);
+      return ERROR;
    }
    if (setjmp(png_jmpbuf((*png_ptr))))
    {
       png_destroy_read_struct(png_ptr, info_ptr, NULL);
-      return (ERROR);
+      return ERROR;
    }
 
    /* You will need to provide all three function callbacks,
@@ -632,7 +632,7 @@ initialize_png_reader(png_structp *png_ptr, png_infop *info_ptr)
     */
    png_set_progressive_read_fn(*png_ptr, (void *)stream_data,
        info_callback, row_callback, end_callback);
-   return (OK);
+   return OK;
 }
 
 int
@@ -643,7 +643,7 @@ process_data(png_structp *png_ptr, png_infop *info_ptr,
    {
       /* Free the png_ptr and info_ptr memory on error. */
       png_destroy_read_struct(png_ptr, info_ptr, NULL);
-      return (ERROR);
+      return ERROR;
    }
 
    /* Give chunks of data as they arrive from the data stream
@@ -657,7 +657,7 @@ process_data(png_structp *png_ptr, png_infop *info_ptr,
     * callback, if you aren't already displaying them there.
     */
    png_process_data(*png_ptr, *info_ptr, buffer, length);
-   return (OK);
+   return OK;
 }
 
 info_callback(png_structp png_ptr, png_infop info)
@@ -747,7 +747,7 @@ void write_png(char *file_name /* , ... other image information ... */)
    /* Open the file */
    fp = fopen(file_name, "wb");
    if (fp == NULL)
-      return (ERROR);
+      return ERROR;
 
    /* Create and initialize the png_struct with the desired error handler
     * functions.  If you want to use the default stderr and longjump method,
@@ -760,7 +760,7 @@ void write_png(char *file_name /* , ... other image information ... */)
    if (png_ptr == NULL)
    {
       fclose(fp);
-      return (ERROR);
+      return ERROR;
    }
 
    /* Allocate/initialize the image information data.  REQUIRED. */
@@ -769,7 +769,7 @@ void write_png(char *file_name /* , ... other image information ... */)
    {
       fclose(fp);
       png_destroy_write_struct(&png_ptr,  NULL);
-      return (ERROR);
+      return ERROR;
    }
 
    /* Set up error handling.  REQUIRED if you aren't supplying your own
@@ -780,7 +780,7 @@ void write_png(char *file_name /* , ... other image information ... */)
       /* If we get here, we had a problem writing the file. */
       fclose(fp);
       png_destroy_write_struct(&png_ptr, &info_ptr);
-      return (ERROR);
+      return ERROR;
    }
 
    /* One of the following I/O initialization functions is REQUIRED. */
@@ -1035,7 +1035,7 @@ void write_png(char *file_name /* , ... other image information ... */)
    fclose(fp);
 
    /* That's it! */
-   return (OK);
+   return OK;
 }
 
 #endif /* if 0 */

png.c

@@ -59,15 +59,15 @@ png_sig_cmp(png_const_bytep sig, size_t start, size_t num_to_check)
       num_to_check = 8;
 
    else if (num_to_check < 1)
-      return (-1);
+      return -1;
 
    if (start > 7)
-      return (-1);
+      return -1;
 
    if (start + num_to_check > 8)
       num_to_check = 8 - start;
 
-   return ((int)(memcmp(&sig[start], &png_signature[start], num_to_check)));
+   return memcmp(&sig[start], &png_signature[start], num_to_check);
 }
 
 #endif /* READ */
@@ -665,9 +665,9 @@ png_voidp PNGAPI
 png_get_io_ptr(png_const_structrp png_ptr)
 {
    if (png_ptr == NULL)
-      return (NULL);
+      return NULL;
 
-   return (png_ptr->io_ptr);
+   return png_ptr->io_ptr;
 }
 
 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)
@@ -956,7 +956,7 @@ png_reset_zstream(png_structrp png_ptr)
       return Z_STREAM_ERROR;
 
    /* WARNING: this resets the window bits to the maximum! */
-   return (inflateReset(&png_ptr->zstream));
+   return inflateReset(&png_ptr->zstream);
 }
 #endif /* READ */
 
@@ -965,7 +965,7 @@ png_uint_32 PNGAPI
 png_access_version_number(void)
 {
    /* Version of *.c files used when building libpng */
-   return((png_uint_32)PNG_LIBPNG_VER);
+   return (png_uint_32)PNG_LIBPNG_VER;
 }
 
 #if defined(PNG_READ_SUPPORTED) || defined(PNG_WRITE_SUPPORTED)

png.h

@@ -908,15 +908,15 @@ PNG_EXPORT(2, void, png_set_sig_bytes, (png_structrp png_ptr, int num_bytes));
 /* Check sig[start] through sig[start + num_to_check - 1] to see if it's a
  * PNG file.  Returns zero if the supplied bytes match the 8-byte PNG
  * signature, and non-zero otherwise.  Having num_to_check == 0 or
- * start > 7 will always fail (ie return non-zero).
+ * start > 7 will always fail (i.e. return non-zero).
  */
 PNG_EXPORT(3, int, png_sig_cmp, (png_const_bytep sig, size_t start,
     size_t num_to_check));
 
 /* Simple signature checking function.  This is the same as calling
- * png_check_sig(sig, n) := !png_sig_cmp(sig, 0, n).
+ * png_check_sig(sig, n) := (png_sig_cmp(sig, 0, n) != 0).
  */
-#define png_check_sig(sig, n) !png_sig_cmp((sig), 0, (n))
+#define png_check_sig(sig, n) (png_sig_cmp((sig), 0, (n)) != 0)
 
 /* Allocate and initialize png_ptr struct for reading, and any other memory. */
 PNG_EXPORTA(4, png_structp, png_create_read_struct,

pngerror.c

@@ -1,7 +1,7 @@
 
 /* pngerror.c - stub functions for i/o and memory allocation
  *
- * Copyright (c) 2018 Cosmin Truta
+ * Copyright (c) 2018-2024 Cosmin Truta
  * Copyright (c) 1998-2002,2004,2006-2017 Glenn Randers-Pehrson
  * Copyright (c) 1996-1997 Andreas Dilger
  * Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.
@@ -858,7 +858,7 @@ png_get_error_ptr(png_const_structrp png_ptr)
    if (png_ptr == NULL)
       return NULL;
 
-   return ((png_voidp)png_ptr->error_ptr);
+   return (png_voidp)png_ptr->error_ptr;
 }