Unpack jv values into Python values directly

Instead of dumping and parsing JSON, convert JQ's "jv" structures into
Python values directly by recursively walking them. The naive
implementation is still twice as fast.

Author: spbnick

jq.pyx

@@ -26,6 +26,15 @@ cdef extern from "jv.h":
     int jv_invalid_has_msg(jv)
     char* jv_string_value(jv)
     jv jv_dump_string(jv, int flags)
+    int jv_is_integer(jv)
+    double jv_number_value(jv)
+    int jv_array_length(jv)
+    jv jv_array_get(jv, int)
+    int jv_object_iter(jv)
+    int jv_object_iter_next(jv, int)
+    int jv_object_iter_valid(jv, int)
+    jv jv_object_iter_key(jv, int)
+    jv jv_object_iter_value(jv, int)
 
     cdef struct jv_parser:
         pass
@@ -51,6 +60,52 @@ cdef extern from "jq.h":
     void jq_get_error_cb(jq_state *, jq_err_cb *, void **)
 
 
+cdef object _jv_to_python(jv value):
+    """Unpack a jv value into a Python value"""
+    cdef jv_kind kind = jv_get_kind(value)
+    cdef int idx
+    cdef jv idx_key
+    cdef jv idx_value
+    cdef object python_value
+
+    if kind == JV_KIND_INVALID:
+        raise ValueError("Invalid value")
+    elif kind == JV_KIND_NULL:
+        python_value = None
+    elif kind == JV_KIND_FALSE:
+        python_value = False
+    elif kind == JV_KIND_TRUE:
+        python_value = True
+    elif kind == JV_KIND_NUMBER:
+        if jv_is_integer(value):
+            python_value = int(jv_number_value(value))
+        else:
+            python_value = float(jv_number_value(value))
+    elif kind == JV_KIND_STRING:
+        python_value = jv_string_value(value).decode("utf-8")
+    elif kind == JV_KIND_ARRAY:
+        python_value = []
+        for idx in range(0, jv_array_length(jv_copy(value))):
+            idx_value = jv_array_get(jv_copy(value), idx)
+            python_value.append(_jv_to_python(idx_value))
+    elif kind == JV_KIND_OBJECT:
+        python_value = {}
+        idx = jv_object_iter(value)
+        while jv_object_iter_valid(value, idx):
+            idx_key = jv_object_iter_key(value, idx)
+            idx_value = jv_object_iter_value(value, idx)
+            try:
+                python_value[jv_string_value(idx_key).decode("utf-8")] = \
+                    _jv_to_python(idx_value)
+            finally:
+                jv_free(idx_key)
+            idx = jv_object_iter_next(value, idx)
+    else:
+        raise ValueError("Invalid value kind: " + str(kind))
+    jv_free(value)
+    return python_value
+
+
 def compile(object program):
     cdef object program_bytes = program.encode("utf8")
     return _Program(program_bytes)
@@ -239,21 +294,34 @@ cdef class _ResultIterator(object):
         return self
 
     def __next__(self):
-        return json.loads(self._next_string())
+        cdef jv value
+        self._next_jv(&value)
+        return _jv_to_python(value)
 
     cdef unicode _next_string(self):
         cdef int dumpopts = 0
+        cdef jv value
+        cdef jv dump
+
+        self._next_jv(&value)
+        dump = jv_dump_string(value, dumpopts)
+        try:
+            string = jv_string_value(dump).decode("utf8")
+        finally:
+            jv_free(dump)
+
+        return string
+
+    cdef int _next_jv(self, jv *presult) except 1:
         while True:
             if not self._ready:
                 self._ready_next_input()
                 self._ready = True
 
             result = jq_next(self._jq)
             if jv_is_valid(result):
-                dumped = jv_dump_string(result, dumpopts)
-                value = jv_string_value(dumped).decode("utf8")
-                jv_free(dumped)
-                return value
+                presult[0] = result
+                return 0
             elif jv_invalid_has_msg(jv_copy(result)):
                 error_message = jv_invalid_get_msg(result)
                 message = jv_string_value(error_message).decode("utf8")