tools/pyboard.py: Add fs_{listdir,readfile,writefile,stat}.

These are for working with the filesystem when using pyboard.py as a
library, rather than at the command line.

- fs_listdir returns a list of tuples, in the same format as os.ilistdir().
- fs_readfile returns the contents of a file as a bytes object.
- fs_writefile allows writing a bytes object to a file.
- fs_stat returns an os.statresult.

All raise FileNotFoundError (or OSError(ENOENT) on Python 2) if the file is
not found (or PyboardError on other errors).

Updated fs_cp and fs_get to use fs_stat to compute file size.

This work was funded through GitHub Sponsors.
Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

tools/pyboard.py

@@ -73,6 +73,8 @@ import struct
 import sys
 import time
 
+from collections import namedtuple
+
 try:
     stdout = sys.stdout.buffer
 except AttributeError:
@@ -87,7 +89,15 @@ def stdout_write_bytes(b):
 
 
 class PyboardError(Exception):
-    pass
+    def convert(self, info):
+        if len(self.args) >= 3:
+            if b"OSError" in self.args[2] and b"ENOENT" in self.args[2]:
+                return OSError(errno.ENOENT, info)
+
+        return self
+
+
+listdir_result = namedtuple("dir_result", ["name", "st_mode", "st_ino", "st_size"])
 
 
 class TelnetToSerial:
@@ -467,6 +477,7 @@ class Pyboard:
             ret = ret.strip()
             return ret
 
+    # In Python3, call as pyboard.exec(), see the setattr call below.
     def exec_(self, command, data_consumer=None):
         ret, ret_err = self.exec_raw(command, data_consumer=data_consumer)
         if ret_err:
@@ -497,6 +508,34 @@ class Pyboard:
         )
         self.exec_(cmd, data_consumer=stdout_write_bytes)
 
+    def fs_listdir(self, src=""):
+        buf = bytearray()
+
+        def repr_consumer(b):
+            buf.extend(b.replace(b"\x04", b""))
+
+        cmd = "import uos\nfor f in uos.ilistdir(%s):\n" " print(repr(f), end=',')" % (
+            ("'%s'" % src) if src else ""
+        )
+        try:
+            buf.extend(b"[")
+            self.exec_(cmd, data_consumer=repr_consumer)
+            buf.extend(b"]")
+        except PyboardError as e:
+            raise e.convert(src)
+
+        return [
+            listdir_result(*f) if len(f) == 4 else listdir_result(*(f + (0,)))
+            for f in ast.literal_eval(buf.decode())
+        ]
+
+    def fs_stat(self, src):
+        try:
+            self.exec_("import uos")
+            return os.stat_result(self.eval("uos.stat(%s)" % (("'%s'" % src)), parse=True))
+        except PyboardError as e:
+            raise e.convert(src)
+
     def fs_cat(self, src, chunk_size=256):
         cmd = (
             "with open('%s') as f:\n while 1:\n"
@@ -504,9 +543,33 @@ class Pyboard:
         )
         self.exec_(cmd, data_consumer=stdout_write_bytes)
 
+    def fs_readfile(self, src, chunk_size=256):
+        buf = bytearray()
+
+        def repr_consumer(b):
+            buf.extend(b.replace(b"\x04", b""))
+
+        cmd = (
+            "with open('%s', 'rb') as f:\n while 1:\n"
+            "  b=f.read(%u)\n  if not b:break\n  print(b,end='')" % (src, chunk_size)
+        )
+        try:
+            self.exec_(cmd, data_consumer=repr_consumer)
+        except PyboardError as e:
+            raise e.convert(src)
+        return ast.literal_eval(buf.decode())
+
+    def fs_writefile(self, dest, data, chunk_size=256):
+        self.exec_("f=open('%s','wb')\nw=f.write" % dest)
+        while data:
+            chunk = data[:chunk_size]
+            self.exec_("w(" + repr(chunk) + ")")
+            data = data[len(chunk) :]
+        self.exec_("f.close()")
+
     def fs_cp(self, src, dest, chunk_size=256, progress_callback=None):
         if progress_callback:
-            src_size = int(self.exec_("import os\nprint(os.stat('%s')[6])" % src))
+            src_size = self.fs_stat(src).st_size
             written = 0
         self.exec_("fr=open('%s','rb')\nr=fr.read\nfw=open('%s','wb')\nw=fw.write" % (src, dest))
         while True:
@@ -520,7 +583,7 @@ class Pyboard:
 
     def fs_get(self, src, dest, chunk_size=256, progress_callback=None):
         if progress_callback:
-            src_size = int(self.exec_("import os\nprint(os.stat('%s')[6])" % src))
+            src_size = self.fs_stat(src).st_size
             written = 0
         self.exec_("f=open('%s','rb')\nr=f.read" % src)
         with open(dest, "wb") as f: