From: Gerhard Sittig <redacted>
Date: Thu, 11 Jun 2020 15:19:50 +0000 (+0200)
Subject: libsigrok-internal: add endianess helpers for floating point types
X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=daa895cba3836f3bd5e02b845f85e23854dff820;p=libsigrok.git

libsigrok-internal: add endianess helpers for floating point types

Extend the common set of endianess conversion helpers. Cover readers and
writers for little endian single and double precision and 64bit integer
values, including support to advance the read/write position.
---

diff --git a/src/libsigrok-internal.h b/src/libsigrok-internal.h
index de338888..339c43bc 100644
--- a/src/libsigrok-internal.h
+++ b/src/libsigrok-internal.h
@@ -312,7 +312,7 @@ static inline int64_t read_i64le(const uint8_t *p)
 #define RL64S(x) read_i64le((const uint8_t *)(x))
 
 /**
- * Read a 32 bits big endian float out of memory.
+ * Read a 32 bits big endian float out of memory (single precision).
  * @param x a pointer to the input memory
  * @return the corresponding float
  */
@@ -335,7 +335,7 @@ static inline float read_fltbe(const uint8_t *p)
 #define RBFL(x) read_fltbe((const uint8_t *)(x))
 
 /**
- * Read a 32 bits little endian float out of memory.
+ * Read a 32 bits little endian float out of memory (single precision).
  * @param x a pointer to the input memory
  * @return the corresponding float
  */
@@ -357,6 +357,29 @@ static inline float read_fltle(const uint8_t *p)
 }
 #define RLFL(x) read_fltle((const uint8_t *)(x))
 
+/**
+ * Read a 64 bits little endian float out of memory (double precision).
+ * @param x a pointer to the input memory
+ * @return the corresponding floating point value
+ */
+static inline double read_dblle(const uint8_t *p)
+{
+	/*
+	 * Implementor's note: Strictly speaking the "union" trick
+	 * is not portable. But this phrase was found to work on the
+	 * project's supported platforms, and serve well until a more
+	 * appropriate phrase is found.
+	 */
+	union { uint64_t u64; double flt; } u;
+	double f;
+
+	u.u64 = read_u64le(p);
+	f = u.flt;
+
+	return f;
+}
+#define RLDB(x) read_dblle((const uint8_t *)(x))
+
 /**
  * Write a 8 bits unsigned integer to memory.
  * @param p a pointer to the output memory
@@ -420,6 +443,24 @@ static inline void write_u32le(uint8_t *p, uint32_t x)
 }
 #define WL32(p, x) write_u32le((uint8_t *)(p), (uint32_t)(x))
 
+/**
+ * Write a 64 bits unsigned integer to memory stored as little endian.
+ * @param p a pointer to the output memory
+ * @param x the input unsigned integer
+ */
+static inline void write_u64le(uint8_t *p, uint64_t x)
+{
+	p[0] = x & 0xff; x >>= 8;
+	p[1] = x & 0xff; x >>= 8;
+	p[2] = x & 0xff; x >>= 8;
+	p[3] = x & 0xff; x >>= 8;
+	p[4] = x & 0xff; x >>= 8;
+	p[5] = x & 0xff; x >>= 8;
+	p[6] = x & 0xff; x >>= 8;
+	p[7] = x & 0xff; x >>= 8;
+}
+#define WL64(p, x) write_u64le((uint8_t *)(p), (uint64_t)(x))
+
 /**
  * Write a 32 bits float to memory stored as big endian.
  * @param p a pointer to the output memory
@@ -446,6 +487,19 @@ static inline void write_fltle(uint8_t *p, float x)
 }
 #define WLFL(p, x) write_fltle((uint8_t *)(p), float (x))
 
+/**
+ * Write a 64 bits float to memory stored as little endian.
+ * @param p a pointer to the output memory
+ * @param x the input floating point value
+ */
+static inline void write_dblle(uint8_t *p, double x)
+{
+	union { uint64_t u; double f; } u;
+	u.f = x;
+	write_u64le(p, u.u);
+}
+#define WLDB(p, x) write_dblle((uint8_t *)(p), float (x))
+
 /* Endianess conversion helpers with read/write position increment. */
 
 /**
@@ -584,6 +638,40 @@ static inline uint64_t read_u64le_inc(const uint8_t **p)
 	return v;
 }
 
+/**
+ * Read 32bit float from raw memory (little endian format), increment read position.
+ * @param[in, out] p Pointer into byte stream.
+ * @return Retrieved float value.
+ */
+static inline float read_fltle_inc(const uint8_t **p)
+{
+	float v;
+
+	if (!p || !*p)
+		return 0;
+	v = read_fltle(*p);
+	*p += sizeof(v);
+
+	return v;
+}
+
+/**
+ * Read 64bit float from raw memory (little endian format), increment read position.
+ * @param[in, out] p Pointer into byte stream.
+ * @return Retrieved float value.
+ */
+static inline double read_dblle_inc(const uint8_t **p)
+{
+	double v;
+
+	if (!p || !*p)
+		return 0;
+	v = read_dblle(*p);
+	*p += sizeof(v);
+
+	return v;
+}
+
 /**
  * Write unsigned 8bit integer to raw memory, increment write position.
  * @param[in, out] p Pointer into byte stream.
@@ -649,6 +737,45 @@ static inline void write_u32le_inc(uint8_t **p, uint32_t x)
 	*p += sizeof(x);
 }
 
+/**
+ * Write unsigned 64bit little endian integer to raw memory, increment write position.
+ * @param[in, out] p Pointer into byte stream.
+ * @param[in] x Value to write.
+ */
+static inline void write_u64le_inc(uint8_t **p, uint64_t x)
+{
+	if (!p || !*p)
+		return;
+	write_u64le(*p, x);
+	*p += sizeof(x);
+}
+
+/**
+ * Write single precision little endian float to raw memory, increment write position.
+ * @param[in, out] p Pointer into byte stream.
+ * @param[in] x Value to write.
+ */
+static inline void write_fltle_inc(uint8_t **p, float x)
+{
+	if (!p || !*p)
+		return;
+	write_fltle(*p, x);
+	*p += sizeof(x);
+}
+
+/**
+ * Write double precision little endian float to raw memory, increment write position.
+ * @param[in, out] p Pointer into byte stream.
+ * @param[in] x Value to write.
+ */
+static inline void write_dblle_inc(uint8_t **p, double x)
+{
+	if (!p || !*p)
+		return;
+	write_dblle(*p, x);
+	*p += sizeof(x);
+}
+
 /* Portability fixes for FreeBSD. */
 #ifdef __FreeBSD__
 #define LIBUSB_CLASS_APPLICATION 0xfe