py: Overhaul and simplify printf/pfenv mechanism.

Previous to this patch the printing mechanism was a bit of a tangled
mess.  This patch attempts to consolidate printing into one interface.

All (non-debug) printing now uses the mp_print* family of functions,
mainly mp_printf.  All these functions take an mp_print_t structure as
their first argument, and this structure defines the printing backend
through the "print_strn" function of said structure.

Printing from the uPy core can reach the platform-defined print code via
two paths: either through mp_sys_stdout_obj (defined pert port) in
conjunction with mp_stream_write; or through the mp_plat_print structure
which uses the MP_PLAT_PRINT_STRN macro to define how string are printed
on the platform.  The former is only used when MICROPY_PY_IO is defined.

With this new scheme printing is generally more efficient (less layers
to go through, less arguments to pass), and, given an mp_print_t*
structure, one can call mp_print_str for efficiency instead of
mp_printf("%s", ...).  Code size is also reduced by around 200 bytes on
Thumb2 archs.

1 files changed, 9 insertions, 28 deletions

diff --git a/py/vstr.c b/py/vstr.c
index 953e8edb5..45915e7c4 100644
--- a/py/vstr.c
+++ b/py/vstr.c
@@ -31,6 +31,7 @@
 
 #include "py/mpconfig.h"
 #include "py/misc.h"
+#include "py/mpprint.h"
 
 // returned value is always at least 1 greater than argument
 #define ROUND_ALLOC(a) (((a) & ((~0) - 7)) + 8)
@@ -65,6 +66,12 @@ void vstr_init_fixed_buf(vstr_t *vstr, size_t alloc, char *buf) {
     vstr->fixed_buf = true;
 }
 
+void vstr_init_print(vstr_t *vstr, size_t alloc, mp_print_t *print) {
+    vstr_init(vstr, alloc);
+    print->data = vstr;
+    print->print_strn = (mp_print_strn_t)vstr_add_strn;
+}
+
 void vstr_clear(vstr_t *vstr) {
     if (!vstr->fixed_buf) {
         m_del(char, vstr->buf, vstr->alloc);
@@ -322,32 +329,6 @@ void vstr_vprintf(vstr_t *vstr, const char *fmt, va_list ap) {
         return;
     }
 
-    while (1) {
-        // try to print in the allocated space
-        // need to make a copy of the va_list because we may call vsnprintf multiple times
-        size_t size = vstr->alloc - vstr->len;
-        va_list ap2;
-        va_copy(ap2, ap);
-        int n = vsnprintf(vstr->buf + vstr->len, size, fmt, ap2);
-        va_end(ap2);
-
-        // if that worked, return
-        if (n > -1 && (size_t)n < size) {
-            vstr->len += n;
-            return;
-        }
-
-        // else try again with more space
-        if (n > -1) { // glibc 2.1
-            // n + 1 is precisely what is needed
-            if (!vstr_ensure_extra(vstr, n + 1)) {
-                return;
-            }
-        } else { // glibc 2.0
-            // increase to twice the old size
-            if (!vstr_ensure_extra(vstr, size * 2)) {
-                return;
-            }
-        }
-    }
+    mp_print_t print = {vstr, (mp_print_strn_t)vstr_add_strn};
+    mp_vprintf(&print, fmt, ap);
 }