py: Implement mp_format_float for doubles and use where appropriate

This allows using (almost) the same code for printing floats everywhere,
removes the dependency on sprintf and uses just snprintf and
applies an msvc-specific fix for snprintf in a single place so
nan/inf are now printed correctly.

5 files changed, 96 insertions, 65 deletions

diff --git a/py/formatfloat.c b/py/formatfloat.c
index 64f013147..cc0636100 100644
--- a/py/formatfloat.c
+++ b/py/formatfloat.c
@@ -24,10 +24,15 @@
  * THE SOFTWARE.
  */
 
+#include <stdlib.h>
+#include <stdint.h>
+#include "py/formatfloat.h"
+
+#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
 /***********************************************************************
 
-  formatfloat.c  - Ruutine for converting a single-precision floating
-                    point number into a string.
+  Routine for converting a single-precision floating
+  point number into a string.
 
   The code in this funcion was inspired from Fred Bayer's pdouble.c.
   Since pdouble.c was released as Public Domain, I'm releasing this
@@ -39,15 +44,6 @@
 
 ***********************************************************************/
 
-#include <stdlib.h>
-#include <stdint.h>
-
-#include "py/mpconfig.h"
-
-#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
-
-#include "py/formatfloat.h"
-
 // 1 sign bit, 8 exponent bits, and 23 mantissa bits.
 // exponent values 0 and 255 are reserved, exponent can be 1 to 254.
 // exponent is stored with a bias of 127.
@@ -341,4 +337,76 @@ int mp_format_float(float f, char *buf, size_t buf_size, char fmt, int prec, cha
     return s - buf;
 }
 
+#elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
+
+#include <errno.h>
+#include <stdio.h>
+
+#ifdef _MSC_VER
+// For msvc we need to address some quirks in the snprintf implementation:
+// - there is no standard snprintf, it is named _snprintf instead
+// - 'F' format isn't handled so use 'f'
+// - nan and inf are printed as 1.#QNAN and 1.#INF
+#include <math.h>
+#include <string.h>
+
+STATIC int copy_with_sign(char *dest, size_t bufSize, const char *value, char sign) {
+    if (bufSize == 0) {
+        return 0;
+    }
+    size_t numSignChars = 0;
+    if (sign) {
+        *dest = sign;
+        ++numSignChars;
+    }
+    // check total length including terminator
+    size_t length = strlen(value) + 1 + numSignChars;
+    if (length > bufSize) {
+        length = bufSize;
+    }
+    // length without terminator
+    --length;
+    if (length > numSignChars) {
+        memcpy(dest + numSignChars, value, length - numSignChars);
+    }
+    dest[length] = 0;
+    return length;
+}
+
+#define snprintf _snprintf
+#endif
+
+int mp_format_float(double value, char *buf, size_t bufSize, char fmt, int prec, char sign) {
+    if (!buf) {
+        errno = EINVAL;
+        return -1;
+    }
+#ifdef _MSC_VER
+    if (isnan(value)) {
+        return copy_with_sign(buf, bufSize, "nan", sign);
+    } else if (isinf(value)) {
+        return copy_with_sign(buf, bufSize, "inf", value > 0.0 ? sign : '-');
+    } else {
+        if (fmt == 'F') {
+            fmt = 'f';
+        }
+#endif
+        char fmt_buf[6];
+        char *fmt_s = fmt_buf;
+
+        *fmt_s++ = '%';
+        if (sign) {
+            *fmt_s++ = sign;
+        }
+        *fmt_s++ = '.';
+        *fmt_s++ = '*';
+        *fmt_s++ = fmt;
+        *fmt_s = '\0';
+
+        return snprintf(buf, bufSize, fmt_buf, prec, value);
+#ifdef _MSC_VER
+    }
+#endif
+}
+
 #endif
diff --git a/py/formatfloat.h b/py/formatfloat.h
index 1eb2c1e46..019603447 100644
--- a/py/formatfloat.h
+++ b/py/formatfloat.h
@@ -26,6 +26,10 @@
 #ifndef __MICROPY_INCLUDED_PY_FORMATFLOAT_H__
 #define __MICROPY_INCLUDED_PY_FORMATFLOAT_H__
 
-int mp_format_float(float f, char *buf, size_t bufSize, char fmt, int prec, char sign);
+#include "py/mpconfig.h"
+
+#if MICROPY_PY_BUILTINS_FLOAT
+int mp_format_float(mp_float_t f, char *buf, size_t bufSize, char fmt, int prec, char sign);
+#endif
 
 #endif // __MICROPY_INCLUDED_PY_FORMATFLOAT_H__
diff --git a/py/mpprint.c b/py/mpprint.c
index 99d0357af..78a0b7aa5 100644
--- a/py/mpprint.c
+++ b/py/mpprint.c
@@ -35,10 +35,6 @@
 #include "py/objint.h"
 #include "py/runtime.h"
 
-#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
-#include <stdio.h>
-#endif
-
 #if MICROPY_PY_BUILTINS_FLOAT
 #include "py/formatfloat.h"
 #endif
@@ -340,29 +336,12 @@ int mp_print_float(const mp_print_t *print, mp_float_t f, char fmt, int flags, c
     if (flags & PF_FLAG_SPACE_SIGN) {
         sign = ' ';
     }
-    int len;
-#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
-    len = mp_format_float(f, buf, sizeof(buf), fmt, prec, sign);
-#elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
-    char fmt_buf[6];
-    char *fmt_s = fmt_buf;
 
-    *fmt_s++ = '%';
-    if (sign) {
-        *fmt_s++ = sign;
-    }
-    *fmt_s++ = '.';
-    *fmt_s++ = '*';
-    *fmt_s++ = fmt;
-    *fmt_s = '\0';
-
-    len = snprintf(buf, sizeof(buf), fmt_buf, prec, f);
+    int len = mp_format_float(f, buf, sizeof(buf), fmt, prec, sign);
     if (len < 0) {
         len = 0;
     }
-#else
-#error Unknown MICROPY FLOAT IMPL
-#endif
+
     char *s = buf;
 
     if ((flags & PF_FLAG_ADD_PERCENT) && (size_t)(len + 1) < sizeof(buf)) {
diff --git a/py/objcomplex.c b/py/objcomplex.c
index 8a424f7f2..b790b0563 100644
--- a/py/objcomplex.c
+++ b/py/objcomplex.c
@@ -37,10 +37,7 @@
 #if MICROPY_PY_BUILTINS_COMPLEX
 
 #include <math.h>
-
-#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
 #include "py/formatfloat.h"
-#endif
 
 typedef struct _mp_obj_complex_t {
     mp_obj_base_t base;
@@ -53,33 +50,23 @@ STATIC void complex_print(const mp_print_t *print, mp_obj_t o_in, mp_print_kind_
     mp_obj_complex_t *o = o_in;
 #if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
     char buf[16];
-    if (o->real == 0) {
-        mp_format_float(o->imag, buf, sizeof(buf), 'g', 7, '\0');
-        mp_printf(print, "%sj", buf);
-    } else {
-        mp_format_float(o->real, buf, sizeof(buf), 'g', 7, '\0');
-        mp_printf(print, "(%s", buf);
-        if (o->imag >= 0 || isnan(o->imag)) {
-            mp_print_str(print, "+");
-        }
-        mp_format_float(o->imag, buf, sizeof(buf), 'g', 7, '\0');
-        mp_printf(print, "%sj)", buf);
-    }
+    const int precision = 7;
 #else
     char buf[32];
+    const int precision = 16;
+#endif
     if (o->real == 0) {
-        sprintf(buf, "%.16g", (double)o->imag);
+        mp_format_float(o->imag, buf, sizeof(buf), 'g', precision, '\0');
         mp_printf(print, "%sj", buf);
     } else {
-        sprintf(buf, "%.16g", (double)o->real);
+        mp_format_float(o->real, buf, sizeof(buf), 'g', precision, '\0');
         mp_printf(print, "(%s", buf);
         if (o->imag >= 0 || isnan(o->imag)) {
             mp_print_str(print, "+");
         }
-        sprintf(buf, "%.16g", (double)o->imag);
+        mp_format_float(o->imag, buf, sizeof(buf), 'g', precision, '\0');
         mp_printf(print, "%sj)", buf);
     }
-#endif
 }
 
 STATIC mp_obj_t complex_make_new(mp_obj_t type_in, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args) {
diff --git a/py/objfloat.c b/py/objfloat.c
index f74e12f9d..ffb3c7196 100644
--- a/py/objfloat.c
+++ b/py/objfloat.c
@@ -37,31 +37,24 @@
 #if MICROPY_PY_BUILTINS_FLOAT
 
 #include <math.h>
-
-#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
 #include "py/formatfloat.h"
-#endif
 
 STATIC void float_print(const mp_print_t *print, mp_obj_t o_in, mp_print_kind_t kind) {
     (void)kind;
     mp_obj_float_t *o = o_in;
 #if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
     char buf[16];
-    mp_format_float(o->value, buf, sizeof(buf), 'g', 7, '\0');
-    mp_print_str(print, buf);
-    if (strchr(buf, '.') == NULL && strchr(buf, 'e') == NULL && strchr(buf, 'n') == NULL) {
-        // Python floats always have decimal point (unless inf or nan)
-        mp_print_str(print, ".0");
-    }
+    const int precision = 7;
 #else
     char buf[32];
-    sprintf(buf, "%.16g", (double) o->value);
+    const int precision = 16;
+#endif
+    mp_format_float(o->value, buf, sizeof(buf), 'g', precision, '\0');
     mp_print_str(print, buf);
     if (strchr(buf, '.') == NULL && strchr(buf, 'e') == NULL && strchr(buf, 'n') == NULL) {
         // Python floats always have decimal point (unless inf or nan)
         mp_print_str(print, ".0");
     }
-#endif
 }
 
 STATIC mp_obj_t float_make_new(mp_obj_t type_in, mp_uint_t n_args, mp_uint_t n_kw, const mp_obj_t *args) {