[RFA][python] Add gdb.Value.string method.

[Thiago Jung Bauermann <bauerman@br.ibm.com>]

Hi,

This patch adds a method to the Value python class which returns the
value as a Python Unicode string. It depends on the patch I just posted
in the "Add la_getstr member to language_defn", and assumes that the
"Fixes and improvements to gdb.Value" patch has been applied. Ok?
-- 
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center


gdb/
2009-01-03  Thiago Jung Bauermann  <bauerman@br.ibm.com>
	    Tom Tromey  <tromey@redhat.com>

	* python/python-utils.c (target_string_to_unicode): New function.
	* python/python-internal.h (target_string_to_unicode): New prototype.
	* python/python-value.c (valpy_string): New function.
	(value_object_methods): Add `string' entry.

gdb/doc/
2009-01-03  Tom Tromey  <tromey@redhat.com>
 
	* gdb.texinfo (Values From Inferior): Document Value.string.

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 030d4b3..3b1cd91 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -18202,6 +18202,31 @@ The result @code{bar} will be a @code{gdb.Value} object holding the
 value pointed to by @code{foo}.
 @end defmethod
 
+@defmethod Value string @r{[}encoding @r{[}errors@r{]}@r{]}
+If this @code{gdb.Value} represents a string, then this method
+converts the contents to a Python string.  Otherwise, this method will
+throw an exception.
+
+Strings are recognized in a language-specific way; whether a given
+@code{gdb.Value} represents a string is determined by the current
+language.
+
+For C-like languages, a value is a string if it is a pointer to or an
+array of characters or ints.  The string is assumed to be terminated
+by a zero of the appropriate width.
+
+If the optional @var{encoding} argument is given, it must be a string
+naming the encoding of the string in the @code{gdb.Value}.  The Python
+codec machinery will be used to convert the string.  If @var{encoding}
+is not given, or if @var{encoding} is the empty string, then either
+the @code{target-charset} (@pxref{Character Sets}) will be used, or a
+language-specific encoding will be used, if the current language is
+able to supply one.
+
+The optional @var{errors} argument is the same as the corresponding
+argument to Python's @code{string.decode} method.
+@end defmethod
+
 @node Interpreters
 @chapter Command Interpreters
 @cindex command interpreters
diff --git a/gdb/python/python-internal.h b/gdb/python/python-internal.h
index bcd37e4..9c2e8c6 100644
--- a/gdb/python/python-internal.h
+++ b/gdb/python/python-internal.h
@@ -88,6 +88,7 @@ PyObject *python_string_to_unicode (PyObject *obj);
 char *unicode_to_target_string (PyObject *unicode_str);
 char *python_string_to_target_string (PyObject *obj);
 char *python_string_to_host_string (PyObject *obj);
+PyObject *target_string_to_unicode (const gdb_byte *str, int length);
 int gdbpy_is_string (PyObject *obj);
 
 #endif /* GDB_PYTHON_INTERNAL_H */
diff --git a/gdb/python/python-utils.c b/gdb/python/python-utils.c
index c27a930..1e6d952 100644
--- a/gdb/python/python-utils.c
+++ b/gdb/python/python-utils.c
@@ -160,6 +160,19 @@ python_string_to_host_string (PyObject *obj)
   return unicode_to_encoded_string (str, host_charset ());
 }
 
+/* Converts a target string of LENGTH bytes in the target's charset to a
+   Python Unicode string. If LENGTH is -1, convert until a null byte is found.
+
+   Returns NULL on error, with a python exception set.  */
+PyObject *
+target_string_to_unicode (const gdb_byte *str, int length)
+{
+  if (length == -1)
+    length = strlen (str);
+
+  return PyUnicode_Decode (str, length, target_charset (), NULL);
+}
+
 /* Return true if OBJ is a Python string or unicode object, false
    otherwise.  */
 
diff --git a/gdb/python/python-value.c b/gdb/python/python-value.c
index 4d1f864..c6775b2 100644
--- a/gdb/python/python-value.c
+++ b/gdb/python/python-value.c
@@ -148,6 +148,47 @@ valpy_address (PyObject *self, PyObject *args)
   return value_to_value_object (res_val);
 }
 
+/* Return Unicode string with value contents (assumed to be encoded in the
+   target's charset).  */
+static PyObject *
+valpy_string (PyObject *self, PyObject *args)
+{
+  int length, ret = 0;
+  gdb_byte *buffer;
+  struct value *value = ((value_object *) self)->value;
+  volatile struct gdb_exception except;
+  PyObject *unicode;
+  const char *encoding = NULL;
+  const char *errors = NULL;
+  const char *user_encoding = NULL;
+  const char *la_encoding = NULL;
+
+  if (!PyArg_ParseTuple (args, "|ss", &user_encoding, &errors))
+    return NULL;
+
+  TRY_CATCH (except, RETURN_MASK_ALL)
+    {
+      ret = LA_GET_STRING (value, &buffer, &length, &la_encoding);
+    }
+  GDB_PY_HANDLE_EXCEPTION (except);
+
+  if (ret != 0)
+    {
+      /* We may have read a partial string before the error happened, but
+         we will ignore it and throw an exception anyway.  */
+      PyErr_SetString (PyExc_RuntimeError, safe_strerror (ret));
+      xfree (buffer);
+
+      return NULL;
+    }
+
+  encoding = (user_encoding && *user_encoding) ? user_encoding : la_encoding;
+  unicode = PyUnicode_Decode (buffer, length, encoding, errors);
+  xfree (buffer);
+
+  return unicode;
+}
+
 static Py_ssize_t
 valpy_length (PyObject *self)
 {
@@ -773,6 +814,8 @@ gdbpy_initialize_values (void)
 static PyMethodDef value_object_methods[] = {
   { "address", valpy_address, METH_NOARGS, "Return the address of the value." },
   { "dereference", valpy_dereference, METH_NOARGS, "Dereferences the value." },
+  { "string", valpy_string, METH_VARARGS,
+    "Return Unicode string representation of the value." },
   {NULL}  /* Sentinel */
 };