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.

3 files changed, 9 insertions, 8 deletions

diff --git a/extmod/moductypes.c b/extmod/moductypes.c
index f9f0ca79b..dff8abd8d 100644
--- a/extmod/moductypes.c
+++ b/extmod/moductypes.c
@@ -137,7 +137,7 @@ STATIC mp_obj_t uctypes_struct_make_new(mp_obj_t type_in, mp_uint_t n_args, mp_u
     return o;
 }
 
-STATIC void uctypes_struct_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
+STATIC void uctypes_struct_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
     (void)kind;
     mp_obj_uctypes_struct_t *self = self_in;
     const char *typen = "unk";
@@ -154,7 +154,7 @@ STATIC void uctypes_struct_print(void (*print)(void *env, const char *fmt, ...),
     } else {
         typen = "ERROR";
     }
-    print(env, "<struct %s %p>", typen, self->addr);
+    mp_printf(print, "<struct %s %p>", typen, self->addr);
 }
 
 // Get size of any type descriptor
diff --git a/extmod/modujson.c b/extmod/modujson.c
index 747a86ac6..d6095cbb8 100644
--- a/extmod/modujson.c
+++ b/extmod/modujson.c
@@ -35,8 +35,9 @@
 
 STATIC mp_obj_t mod_ujson_dumps(mp_obj_t obj) {
     vstr_t vstr;
-    vstr_init(&vstr, 8);
-    mp_obj_print_helper((void (*)(void *env, const char *fmt, ...))vstr_printf, &vstr, obj, PRINT_JSON);
+    mp_print_t print;
+    vstr_init_print(&vstr, 8, &print);
+    mp_obj_print_helper(&print, obj, PRINT_JSON);
     return mp_obj_new_str_from_vstr(&mp_type_str, &vstr);
 }
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(mod_ujson_dumps_obj, mod_ujson_dumps);
diff --git a/extmod/modure.c b/extmod/modure.c
index 66fb51aef..9bc72add2 100644
--- a/extmod/modure.c
+++ b/extmod/modure.c
@@ -51,10 +51,10 @@ typedef struct _mp_obj_match_t {
 } mp_obj_match_t;
 
 
-STATIC void match_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
+STATIC void match_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
     (void)kind;
     mp_obj_match_t *self = self_in;
-    print(env, "<match num=%d>", self->num_matches);
+    mp_printf(print, "<match num=%d>", self->num_matches);
 }
 
 STATIC mp_obj_t match_group(mp_obj_t self_in, mp_obj_t no_in) {
@@ -86,10 +86,10 @@ STATIC const mp_obj_type_t match_type = {
     .locals_dict = (mp_obj_t)&match_locals_dict,
 };
 
-STATIC void re_print(void (*print)(void *env, const char *fmt, ...), void *env, mp_obj_t self_in, mp_print_kind_t kind) {
+STATIC void re_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
     (void)kind;
     mp_obj_re_t *self = self_in;
-    print(env, "<re %p>", self);
+    mp_printf(print, "<re %p>", self);
 }
 
 STATIC mp_obj_t re_exec(bool is_anchored, uint n_args, const mp_obj_t *args) {