From 2c4e4054b3019024ee5fdfa0d69f200704a2d6f6 Mon Sep 17 00:00:00 2001 From: Dale Curtis Date: Thu, 30 Apr 2020 15:16:31 -0700 Subject: [PATCH 2/2] Add saturated add/sub operations for int64_t. Many places are using their own custom code for handling overflow around timestamps or other int64_t values. There are enough of these now that having some common saturated math functions seems sound. Signed-off-by: Dale Curtis --- libavutil/common.h | 46 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 46 insertions(+) diff --git a/libavutil/common.h b/libavutil/common.h index 142ff9abe7..c4f5eea409 100644 --- a/libavutil/common.h +++ b/libavutil/common.h @@ -291,6 +291,46 @@ static av_always_inline int av_sat_dsub32_c(int a, int b) return av_sat_sub32(a, av_sat_add32(b, b)); } +/** + * Add two signed 64-bit values with saturation. + * + * @param a one value + * @param b another value + * @return sum with signed saturation + */ +static av_always_inline int64_t av_sat_add64_c(int64_t a, int64_t b) { +#if AV_GCC_VERSION_AT_LEAST(5,0) || defined(__clang__) + int64_t tmp; + return !__builtin_add_overflow(a, b, &tmp) ? tmp : (tmp < 0 ? INT64_MAX : INT64_MIN); +#else + if (b >= 0 && a >= INT64_MAX - b) + return INT64_MAX; + if (b <= 0 && a <= INT64_MIN - b) + return INT64_MIN; + return a + b; +#endif +} + +/** + * Subtract two signed 64-bit values with saturation. + * + * @param a one value + * @param b another value + * @return difference with signed saturation + */ +static av_always_inline int64_t av_sat_sub64_c(int64_t a, int64_t b) { +#if AV_GCC_VERSION_AT_LEAST(5,0) || defined(__clang__) + int64_t tmp; + return !__builtin_sub_overflow(a, b, &tmp) ? tmp : (tmp < 0 ? INT64_MAX : INT64_MIN); +#else + if (b <= 0 && a >= INT64_MAX + b) { + return INT64_MAX; + if (b >= 0 && a <= INT64_MIN + b) { + return INT64_MIN; + return a - b; +#endif +} + /** * Clip a float value into the amin-amax range. * @param a value to clip @@ -545,6 +585,12 @@ static av_always_inline av_const int av_parity_c(uint32_t v) #ifndef av_sat_dsub32 # define av_sat_dsub32 av_sat_dsub32_c #endif +#ifndef av_sat_add64 +# define av_sat_add64 av_sat_add64_c +#endif +#ifndef av_sat_sub64 +# define av_sat_sub64 av_sat_sub64_c +#endif #ifndef av_clipf # define av_clipf av_clipf_c #endif -- 2.24.1.windows.2