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https://github.com/espressif/ESP8266_RTOS_SDK.git
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100 lines
4.2 KiB
C
100 lines
4.2 KiB
C
// Copyright 2018-2019 Espressif Systems (Shanghai) PTE LTD
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#pragma once
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#include <stdint.h>
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#include <stddef.h>
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/**
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* @brief ESP8266's IBus(instruction bus) only can read data of word type by 4 bytes align,
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* so if users' code read a bytes or half word from IBus, an load/store exception will occure.
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*
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* The exception function will read the word by align and transform it to be the right
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* data that users' code want to read.
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*
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* CPU read data from IRAM or flash by IBus. And "const" type value or string will locate at flash by default.
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* So users' code read "const" type data whose type is byte or half word should lead to exception,
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* and the exception operation is so slow.
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*
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* For example:
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*
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* static const char s_output[] = "123456789";
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*
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* char get_byte(int index)
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* {
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* return s_output(index);
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* }
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*
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* By above way, reading data may be not by 4 bytes align and word type.
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*
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* For this reason, we add the following function to read byte or half word without leading to exception. Firstly the function reads
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* a word and then transform it to be the right data that users' code want to read. Users can modify above code to be following:
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*
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* static const char s_output[] = "123456789";
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*
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* char get_byte(int index)
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* {
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* return ESP_IBUS_GET_U8_DATA(index, s_output);
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* }
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*/
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#ifdef USING_IBUS_FASTER_GET
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#include "esp_attr.h"
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#ifndef DISABLE_IBUS_INLINE_FUNC
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#define IBUS_INLINE inline
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#else
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#define IBUS_INLINE
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#endif
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typedef union _ibus_data {
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uint32_t u32_data[1];
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uint16_t u16_data[2];
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uint8_t u8_data[4];
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} ibus_data_t;
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#define __ESP_IBUS_GET_DATA(_type) \
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static IBUS_INLINE _type __esp_ibus_get_## _type ## _data(size_t index, const void *pbuf) \
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{ \
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ibus_data_t data; \
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const uint8_t num = index / (sizeof(uint32_t) / sizeof(_type)); \
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const uint8_t off = index % (sizeof(uint32_t) / sizeof(_type)); \
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const uint32_t *ptable = (const uint32_t *)pbuf; \
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\
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data.u32_data[0] = ptable[num]; \
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\
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if (sizeof(_type) == sizeof(uint8_t)) \
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return data.u8_data[off]; \
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else if (sizeof(_type) == sizeof(uint16_t)) \
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return data.u16_data[off]; \
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}
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__ESP_IBUS_GET_DATA(uint8_t)
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__ESP_IBUS_GET_DATA(uint16_t)
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#define ESP_IBUS_ATTR WORD_ALIGNED_ATTR
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#define ESP_IBUS_GET_U8_DATA(_index, _pbuf) __esp_ibus_get_uint8_t_data(_index, _pbuf)
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#define ESP_IBUS_GET_U16_DATA(_index, _pbuf) __esp_ibus_get_uint16_t_data(_index, _pbuf)
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#else
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#define ESP_IBUS_ATTR
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#define ESP_IBUS_GET_U8_DATA(_index, _pbuf) ((const uint8_t *)_pbuf)[_index]
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#define ESP_IBUS_GET_U16_DATA(_index, _pbuf) ((const uint16_t *)_pbuf)[_index]
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#endif
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