Add Doxygen-styled comments to parts of the libretro API

libretro-common/include/audio/conversion/float_to_s16.h

@@ -31,22 +31,28 @@ RETRO_BEGIN_DECLS
 #include <stddef.h>
 
 /**
- * convert_float_to_s16:
- * @out               : output buffer
- * @in                : input buffer
- * @samples           : size of samples to be converted
+ * Converts an array of floating-point audio samples
+ * to signed integer 16-bit audio samples,
+ * possibly using SIMD intrinsics.
  *
- * Converts floating point
- * to signed integer 16-bit.
+ * @param out The buffer that will be used to store the converted samples.
+ * @param in The buffer containing the samples to convert.
+ * Any number of channels is supported.
+ * @param samples The length of \c in in samples, \em not bytes or frames.
+ * \c out must be as large as <tt>sizeof(int16_t) * samples</tt>.
+ * @see convert_s16_to_float
  **/
 void convert_float_to_s16(int16_t *out,
       const float *in, size_t samples);
 
 /**
- * convert_float_to_s16_init_simd:
+ * Initializes any prerequisites for
+ * using SIMD implementations of \c convert_float_to_s16.
  *
- * Sets up function pointers for conversion
- * functions based on CPU features.
+ * If SIMD intrinsics are not available or no initialization is required,
+ * this function does nothing.
+ *
+ * @see convert_float_to_s16
  **/
 void convert_float_to_s16_init_simd(void);
 

libretro-common/include/audio/conversion/s16_to_float.h

@@ -30,23 +30,30 @@
 RETRO_BEGIN_DECLS
 
 /**
- * convert_s16_to_float:
- * @out               : output buffer
- * @in                : input buffer
- * @samples           : size of samples to be converted
- * @gain              : gain applied (.e.g. audio volume)
+ * Converts an array of signed integer 16-bit audio samples
+ * to floating-point format,
+ * possibly using SIMD intrinsics.
  *
- * Converts from signed integer 16-bit
- * to floating point.
+ * @param out The buffer that will be used to store the converted samples.
+ * @param in The buffer containing the samples to convert.
+ * Any number of channels is supported.
+ * @param samples The length of \c in in samples, \em not bytes or frames.
+ * \c out must be as large as <tt>sizeof(float) * samples</tt>.
+ * @param gain The gain (audio volume) to apply to the samples.
+ * Pass a value of 1.0 to not apply any gain.
+ * @see convert_float_to_s16
  **/
 void convert_s16_to_float(float *out,
       const int16_t *in, size_t samples, float gain);
 
 /**
- * convert_s16_to_float_init_simd:
+ * Initializes any prerequisites for
+ * using SIMD implementations of \c convert_s16_to_float.
  *
- * Sets up function pointers for conversion
- * functions based on CPU features.
+ * If SIMD intrinsics are not available or no initialization is required,
+ * this function does nothing.
+ *
+ * @see convert_s16_to_float
  **/
 void convert_s16_to_float_init_simd(void);
 

libretro-common/include/clamping.h

@@ -27,14 +27,13 @@
 #include <retro_inline.h>
 
 /**
- * clamp_float:
- * @val           : initial value
- * @lower         : lower limit that value should be clamped against
- * @upper         : upper limit that value should be clamped against
+ * Clamps a floating-point value to the specified range.
  *
- * Clamps a floating point value.
+ * @param val The value to clamp.
+ * @param lower The minimum possible value.
+ * @param upper The maximum possible value.
  *
- * Returns: a clamped value of initial float value @val.
+ * @returns \c val clamped to between \c lower and \c upper (inclusive).
  */
 static INLINE float clamp_float(float val, float lower, float upper)
 {
@@ -46,12 +45,10 @@ static INLINE float clamp_float(float val, float lower, float upper)
 }
 
 /**
- * clamp_8bit:
- * @val           : initial value
+ * Clamps an integer to fit in 8 bits.
  *
- * Clamps an unsigned 8-bit value.
- *
- * Returns: a clamped value of initial unsigned 8-bit value @val.
+ * @param val The value to clamp.
+ * @return \c val clamped to between 0 and 255 (inclusive).
  */
 static INLINE uint8_t clamp_8bit(int val)
 {

libretro-common/include/compat/fnmatch.h

@@ -25,6 +25,11 @@
 
 #define	FNM_NOMATCH	1
 
+/**
+ * Portable implementation of \c fnmatch(3),
+ * except \c flags is not implemented.
+ * @see https://man7.org/linux/man-pages/man3/fnmatch.3.html
+ */
 int rl_fnmatch(const char *pattern, const char *string, int flags);
 
 #endif

libretro-common/include/compat/getopt.h

@@ -27,9 +27,17 @@
 #include "../../../config.h"
 #endif
 
-/* Custom implementation of the GNU getopt_long for portability.
- * Not designed to be fully compatible, but compatible with
- * the features RetroArch uses. */
+/**
+ * @file getopt.h
+ *
+ * Portable reimplementation of a subset of libc's \c getopt_long.
+ * Not designed to be fully compatible,
+ * but it's enough for RetroArch's purposes.
+ *
+ * If \c getopt_long is available (as determined by \c HAVE_GETOPT_LONG), it will be used instead.
+ *
+ * @see https://man7.org/linux/man-pages/man3/getopt.3.html
+ */
 
 #ifdef HAVE_GETOPT_LONG
 #include <getopt.h>

libretro-common/include/compat/ifaddrs.h

@@ -47,7 +47,20 @@ struct ifaddrs
 
 #include <sys/cdefs.h>
 
+/**
+ * Portable reimplementation of \c getifaddrs().
+ * The original function will be used if it's available.
+ *
+ * @see https://man7.org/linux/man-pages/man3/getifaddrs.3.html
+ */
 extern int getifaddrs(struct ifaddrs **ifap);
+
+/**
+ * Portable reimplementation of \c freeifaddrs().
+ * The original function will be used if it's available.
+ *
+ * @see https://man7.org/linux/man-pages/man3/getifaddrs.3.html
+ */
 extern void freeifaddrs(struct ifaddrs *ifa);
 
 #endif

libretro-common/include/compat/intrinsics.h

@@ -38,7 +38,13 @@
 
 RETRO_BEGIN_DECLS
 
-/* Count Leading Zero, unsigned 16bit input value */
+/**
+ * Counts the leading zero bits in a \c uint16_t.
+ * Uses compiler intrinsics if available, or a standard C implementation if not.
+ *
+ * @param val Value to count leading zeroes in.
+ * @return Number of leading zeroes in \c val.
+ */
 static INLINE unsigned compat_clz_u16(uint16_t val)
 {
 #if defined(__GNUC__)
@@ -56,7 +62,13 @@ static INLINE unsigned compat_clz_u16(uint16_t val)
 #endif
 }
 
-/* Count Trailing Zero */
+/**
+ * Counts the trailing zero bits in a \c uint16_t.
+ * Uses compiler intrinsics if available, or a standard C implementation if not.
+ *
+ * @param val Value to count trailing zeroes in.
+ * @return Number of trailing zeroes in \c val.
+ */
 static INLINE int compat_ctz(unsigned x)
 {
 #if defined(__GNUC__) && !defined(RARCH_CONSOLE)

libretro-common/include/compat/posix_string.h

@@ -25,31 +25,64 @@
 
 #include <retro_common_api.h>
 
+/**
+ * @file posix_string.h
+ *
+ * Portable reimplementations of various string functions
+ * that are normally provided by libc or POSIX.
+ */
+
 #ifdef _MSC_VER
 #include <compat/msvc.h>
 #endif
 
 RETRO_BEGIN_DECLS
 
-#ifdef _WIN32
+#if defined(_WIN32) || defined(DOXYGEN)
 #undef strtok_r
 #define strtok_r(str, delim, saveptr) retro_strtok_r__(str, delim, saveptr)
 
+/**
+ * Portable reimplementation of \c strtok_r().
+ * The original function will be used if it's available.
+ *
+ * @see https://man7.org/linux/man-pages/man3/strtok.3.html
+ */
 char *strtok_r(char *str, const char *delim, char **saveptr);
 #endif
 
-#ifdef _MSC_VER
+#if defined(_MSC_VER) || defined(DOXYGEN)
 #undef strcasecmp
 #undef strdup
+
 #define strcasecmp(a, b) retro_strcasecmp__(a, b)
 #define strdup(orig)     retro_strdup__(orig)
+/**
+ * Portable reimplementation of \c strcasecmp().
+ * The original function will be used if it's available.
+ *
+ * @see https://man7.org/linux/man-pages/man3/strcasecmp.3.html
+ */
 int strcasecmp(const char *a, const char *b);
+
+/**
+ * Portable reimplementation of \c strdup().
+ * The original function will be used if it's available.
+ *
+ * @see https://man7.org/linux/man-pages/man3/strdup.3.html
+ */
 char *strdup(const char *orig);
 
 /* isblank is available since MSVC 2013 */
 #if _MSC_VER < 1800
 #undef isblank
 #define isblank(c)       retro_isblank__(c)
+/**
+ * Portable reimplementation of \c isblank().
+ * The original function will be used if it's available.
+ *
+ * @see https://en.cppreference.com/w/c/string/byte/isblank
+ */
 int isblank(int c);
 #endif
 

libretro-common/include/compat/strcasestr.h

@@ -39,6 +39,14 @@ RETRO_BEGIN_DECLS
  * since we prefer to use the actual name. */
 #define strcasestr(haystack, needle) strcasestr_retro__(haystack, needle)
 
+/**
+ * Portable reimplementation of \c strcasestr(3).
+ * If the original function is available
+ * (as determined by the presence of \c HAVE_STRCASESTR),
+ * it will be used instead.
+ *
+ * @see https://man7.org/linux/man-pages/man3/strstr.3.html
+ */
 char *strcasestr(const char *haystack, const char *needle);
 
 RETRO_END_DECLS

libretro-common/include/dynamic/dylib.h

@@ -39,30 +39,79 @@
 
 RETRO_BEGIN_DECLS
 
+/**
+ * Opaque handle to a dynamic library.
+ * @see dylib_load
+ */
 typedef void *dylib_t;
+
+/**
+ * Opaque handle to a function exposed by a dynamic library.
+ *
+ * Should be cast to a known function pointer type before being used.
+ * @see dylib_proc
+ */
 typedef void (*function_t)(void);
 
 #ifdef NEED_DYNAMIC
 /**
- * dylib_load:
- * @path                         : Path to libretro core library.
+ * Loads a dynamic library in a platform-independent manner.
  *
- * Platform independent dylib loading.
+ * @param path Path to the library to load.
+ * May be either a complete path or a filename without an extension.
+ * If not a complete path, the operating system will search for a library by this name;
+ * details will depend on the platform.
+ * @note The returned library must be freed with \c dylib_close
+ * before the core or frontend exits.
  *
- * @return Library handle on success, otherwise NULL.
+ * @return Handle to the loaded library, or \c NULL on failure.
+ * Upon failure, \c dylib_error may be used
+ * to retrieve a string describing the error.
+ * @see dylib_close
+ * @see dylib_error
+ * @see dylib_proc
  **/
 dylib_t dylib_load(const char *path);
 
 /**
- * dylib_close:
- * @lib                          : Library handle.
+ * Frees the resources associated with a dynamic library.
+ *
+ * Any function pointers obtained from the library may become invalid,
+ * depending on whether the operating system manages reference counts to dynamic libraries.
  *
- * Frees library handle.
+ * If there was an error closing the library,
+ * it will be reported by \c dylib_error.
+ *
+ * @param lib Handle to the library to close.
+ * Behavior is undefined if \c NULL.
  **/
 void dylib_close(dylib_t lib);
 
+/**
+ * Returns a string describing the most recent error that occurred
+ * within the other \c dylib functions.
+ *
+ * @return Pointer to the most recent error string,
+ * \c or NULL if there was no error.
+ * @warning The returned string is only valid
+ * until the next call to a \c dylib function.
+ * Additionally, the string is managed by the library
+ * and should not be modified or freed by the caller.
+ */
 char *dylib_error(void);
 
+/**
+ * Returns a pointer to a function exposed by a dynamic library.
+ *
+ * @param lib The library to get a function pointer from.
+ * @param proc The name of the function to get a pointer to.
+ * @return Pointer to the requested function,
+ * or \c NULL if there was an error.
+ * This must be cast to the correct function pointer type before being used.
+ * @warning The returned pointer is only valid for the lifetime of \c lib.
+ * Once \c lib is closed, all function pointers returned from it will be invalidated;
+ * using them is undefined behavior.
+ */
 function_t dylib_proc(dylib_t lib, const char *proc);
 #endif
 

libretro-common/include/encodings/base64.h

@@ -8,7 +8,29 @@
 
 RETRO_BEGIN_DECLS
 
+/**
+ * Encodes binary data into a \c NULL-terminated base64 string.
+ *
+ * @param binaryData The data to encode.
+ * Behavior is undefined if \c NULL.
+ * @param len The length of the data to encode.
+ * @param flen Pointer to the length of the returned string.
+ * @return Pointer to the base64-encoded string, or \c NULL on failure.
+ * The returned string is owned by the caller and must be released with \c free().
+ * @see unbase64
+ */
 char* base64(const void* binaryData, int len, int *flen);
+
+/**
+ * Decodes a base64-encoded string into binary data.
+ *
+ * @param ascii The base64 string to decode, in ASCII format.
+ * @param len Length of the string to decode.
+ * @param flen Pointer to the length of the returned data.
+ * @return The decoded binary data, or \c NULL on failure.
+ * The returned buffer is owned by the caller and must be released with \c free().
+ * @see base64
+ */
 unsigned char* unbase64(const char* ascii, int len, int *flen);
 
 RETRO_END_DECLS