bitops: rename from _bit_transpose, describe the algorithm

3 files changed, 102 insertions, 101 deletions

diff --git a/shared-bindings/_bit_transpose/__init__.c b/shared-bindings/_bit_transpose/__init__.c
deleted file mode 100644
index 0b9d31fbe..000000000
--- a/shared-bindings/_bit_transpose/__init__.c
+++ /dev/null
@@ -1,100 +0,0 @@
-/*
- * This file is part of the Circuit Python project, https://github.com/adafruit/circuitpython
- *
- * The MIT License (MIT)
- *
- * Copyright (c) 2018 Roy Hooper
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-#include "py/obj.h"
-#include "py/runtime.h"
-
-#include "shared-bindings/_bit_transpose/__init__.h"
-
-//| """A fast bit transposition function for parallel NeoPixel strips
-//|
-//| When driving multiple NeoPixel strips from a shift register, the bits
-//| must be re-ordered in a specific way.  This module offers a low-level
-//| routine for performing the transformation."""
-//|
-
-//| def bit_transpose(input: _typing.ReadableBuffer, *, num_strands:int = 8, output: Optional[_typing.WriteableBuffer]=None) -> WriteableBuffer:
-//|     """Convert a sequence of pixel values into a single stream of bytes suitable for sending via a parallel conversion method (PioPixl8)
-//|
-//|     The number of bytes in the input buffer must be a multiple of the number of strands.
-//|
-//|     If specified output buffer must be big enough for the output, ``len(input) * 8  // num_strands``.  To get a properly sized buffer,
-//|     you can also pass in ``output=None`` once, then re-use the return value in future calls.
-//|
-//|     Returns the output buffer if specified (which must be big enough to hold the result), otherwise a freshly allocated buffer."""
-//|     ...
-//|
-STATIC mp_obj_t bit_transpose(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
-    enum { ARG_input, ARG_num_strands, ARG_output };
-    static const mp_arg_t allowed_args[] = {
-        { MP_QSTR_input, MP_ARG_OBJ | MP_ARG_REQUIRED, {} },
-        { MP_QSTR_num_strands, MP_ARG_INT | MP_ARG_KW_ONLY, { .u_int = 8 } },
-        { MP_QSTR_output, MP_ARG_OBJ | MP_ARG_KW_ONLY, { .u_obj = mp_const_none } },
-    };
-    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
-    mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
-
-    mp_buffer_info_t input_bufinfo;
-    mp_buffer_info_t output_bufinfo;
-
-    mp_get_buffer_raise(args[ARG_input].u_obj, &input_bufinfo, MP_BUFFER_READ);
-    int num_strands = args[ARG_num_strands].u_int;
-
-    if (num_strands < 2 || num_strands > 8) {
-        mp_raise_ValueError(translate("num_strands must be from 2 to 8 (inclusive)"));
-    }
-
-    int inlen = input_bufinfo.len;
-    if (inlen % num_strands != 0) {
-        mp_raise_ValueError_varg(translate("Input buffer length (%d) must be a multiple of the strand count (%d)"), inlen, num_strands);
-    }
-    mp_obj_t output = args[ARG_output].u_obj;
-
-    int outlen = 8 * (inlen / num_strands);
-    if (!output || output == mp_const_none) {
-        output = mp_obj_new_bytearray_of_zeros(outlen);
-    }
-    mp_get_buffer_raise(output, &output_bufinfo, MP_BUFFER_WRITE);
-    int avail = output_bufinfo.len;
-    if (avail < outlen) {
-        mp_raise_ValueError_varg(translate("Output buffer must be at least %d bytes"), outlen);
-    }
-    common_hal_bit_transpose_bit_transpose(output_bufinfo.buf, input_bufinfo.buf, inlen, num_strands);
-    return output;
-}
-STATIC MP_DEFINE_CONST_FUN_OBJ_KW(bit_transpose_bit_transpose_obj, 1, bit_transpose);
-
-STATIC const mp_rom_map_elem_t bit_transpose_module_globals_table[] = {
-    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR__bit_transpose) },
-    { MP_ROM_QSTR(MP_QSTR_bit_transpose), MP_ROM_PTR(&bit_transpose_bit_transpose_obj) },
-};
-
-STATIC MP_DEFINE_CONST_DICT(bit_transpose_module_globals, bit_transpose_module_globals_table);
-
-const mp_obj_module_t bit_transpose_module = {
-    .base = { &mp_type_module },
-    .globals = (mp_obj_dict_t*)&bit_transpose_module_globals,
-};
diff --git a/shared-bindings/bitops/__init__.c b/shared-bindings/bitops/__init__.c
new file mode 100644
index 000000000..fc5784259
--- /dev/null
+++ b/shared-bindings/bitops/__init__.c
@@ -0,0 +1,101 @@
+/*
+ * This file is part of the Circuit Python project, https://github.com/adafruit/circuitpython
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2018 Roy Hooper
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "py/obj.h"
+#include "py/runtime.h"
+
+#include "shared-bindings/bitops/__init__.h"
+
+//| """Routines for low-level manipulation of binary data"""
+//|
+//|
+
+//| def bit_transpose(input: _typing.ReadableBuffer, *, width:int = 8, output: Optional[_typing.WriteableBuffer]=None) -> WriteableBuffer:
+//|     """"Transpose" a buffer by assembling each output byte with bits taken from each of ``width`` different input bytes.
+//|
+//|     This can be useful to convert a sequence of pixel values into a single
+//|     stream of bytes suitable for sending via a parallel conversion method.
+//|
+//|     The number of bytes in the input buffer must be a multiple of the width,
+//|     and the width can be any value from 2 to 8.  If the width is fewer than 8,
+//|     then the remaining (less significant) bits of the output are set to zero.
+//|
+//|     Let ``stride = len(input)//width``.  Then the first byte is made out of the
+//|     most significant bits of ``[input[0], input[stride], input[2*stride], ...]``.
+//|     The second byte is made out of the second bits, and so on until the 8th output
+//|     byte which is made of the first bits of ``input[1], input[1+stride,
+//|     input[2*stride], ...]``.
+//|
+//|     The required output buffer size is ``len(input) * 8  // width``.
+//|
+//|     Returns the output buffer."""
+//|     ...
+
+STATIC mp_obj_t bit_transpose(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_input, ARG_width, ARG_output };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_input, MP_ARG_OBJ | MP_ARG_REQUIRED },
+        { MP_QSTR_output, MP_ARG_OBJ | MP_ARG_REQUIRED },
+        { MP_QSTR_width, MP_ARG_INT | MP_ARG_KW_ONLY, { .u_int = 8 } },
+    };
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    int width = args[ARG_width].u_int;
+    if (width < 2 || width > 8) {
+        mp_raise_ValueError(translate("width must be from 2 to 8 (inclusive)"));
+    }
+
+    mp_buffer_info_t input_bufinfo;
+    mp_get_buffer_raise(args[ARG_input].u_obj, &input_bufinfo, MP_BUFFER_READ);
+    int inlen = input_bufinfo.len;
+    if (inlen % width != 0) {
+        mp_raise_ValueError_varg(translate("Input buffer length (%d) must be a multiple of the strand count (%d)"), inlen, width);
+    }
+
+    mp_buffer_info_t output_bufinfo;
+    mp_get_buffer_raise(args[ARG_output].u_obj, &output_bufinfo, MP_BUFFER_WRITE);
+    int avail = output_bufinfo.len;
+    int outlen = 8 * (inlen / width);
+    if (avail < outlen) {
+        mp_raise_ValueError_varg(translate("Output buffer must be at least %d bytes"), outlen);
+    }
+    common_hal_bitops_bit_transpose(output_bufinfo.buf, input_bufinfo.buf, inlen, width);
+    return args[ARG_output].u_obj;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_KW(bitops_bit_transpose_obj, 1, bit_transpose);
+
+STATIC const mp_rom_map_elem_t bitops_module_globals_table[] = {
+    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_bitops) },
+    { MP_ROM_QSTR(MP_QSTR_bit_transpose), MP_ROM_PTR(&bitops_bit_transpose_obj) },
+};
+
+STATIC MP_DEFINE_CONST_DICT(bitops_module_globals, bitops_module_globals_table);
+
+const mp_obj_module_t bitops_module = {
+    .base = { &mp_type_module },
+    .globals = (mp_obj_dict_t*)&bitops_module_globals,
+};
diff --git a/shared-bindings/_bit_transpose/__init__.h b/shared-bindings/bitops/__init__.h
index 5fcf11d45..6654cac5e 100644
--- a/shared-bindings/_bit_transpose/__init__.h
+++ b/shared-bindings/bitops/__init__.h
@@ -29,4 +29,4 @@
 #include <stdint.h>
 #include <stdlib.h>
 
-void common_hal_bit_transpose_bit_transpose(uint8_t *result, const uint8_t *src, size_t inlen, size_t num_strands);
+void common_hal_bitops_bit_transpose(uint8_t *result, const uint8_t *src, size_t inlen, size_t num_strands);