1 |
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2 | /*
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3 | * Copyright (c) 2015-2016, ARM Limited, All Rights Reserved
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4 | * SPDX-License-Identifier: Apache-2.0
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5 | *
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6 | * Licensed under the Apache License, Version 2.0 (the "License"); you may
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7 | * not use this file except in compliance with the License.
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8 | * You may obtain a copy of the License at
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9 | *
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10 | * http://www.apache.org/licenses/LICENSE-2.0
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11 | *
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12 | * Unless required by applicable law or agreed to in writing, software
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13 | * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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14 | * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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15 | * See the License for the specific language governing permissions and
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16 | * limitations under the License.
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17 | */
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18 |
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19 | #ifndef __MBED_UTIL_CRITICAL_H__
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20 | #define __MBED_UTIL_CRITICAL_H__
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21 |
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22 | #include <stdbool.h>
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23 | #include <stdint.h>
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24 | #include <stddef.h>
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25 |
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26 | #ifdef __cplusplus
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27 | extern "C" {
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28 | #endif
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29 |
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30 | /** \addtogroup platform */
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31 | /** @{*/
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32 | /**
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33 | * \defgroup platform_critical critical section function
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34 | * @{
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35 | */
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36 |
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37 | /** Determine the current interrupts enabled state
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38 | *
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39 | * This function can be called to determine whether or not interrupts are currently enabled.
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40 | * @note
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41 | * NOTE:
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42 | * This function works for both cortex-A and cortex-M, although the underlyng implementation
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43 | * differs.
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44 | * @return true if interrupts are enabled, false otherwise
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45 | */
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46 | bool core_util_are_interrupts_enabled(void);
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47 |
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48 | /** Determine if this code is executing from an interrupt
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49 | *
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50 | * This function can be called to determine if the code is running on interrupt context.
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51 | * @note
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52 | * NOTE:
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53 | * This function works for both cortex-A and cortex-M, although the underlyng implementation
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54 | * differs.
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55 | * @return true if in an isr, false otherwise
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56 | */
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57 | bool core_util_is_isr_active(void);
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58 |
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59 | /** Mark the start of a critical section
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60 | *
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61 | * This function should be called to mark the start of a critical section of code.
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62 | * @note
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63 | * NOTES:
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64 | * 1) The use of this style of critical section is targetted at C based implementations.
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65 | * 2) These critical sections can be nested.
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66 | * 3) The interrupt enable state on entry to the first critical section (of a nested set, or single
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67 | * section) will be preserved on exit from the section.
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68 | * 4) This implementation will currently only work on code running in privileged mode.
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69 | */
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70 | void core_util_critical_section_enter(void);
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71 |
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72 | /** Mark the end of a critical section
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73 | *
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74 | * This function should be called to mark the end of a critical section of code.
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75 | * @note
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76 | * NOTES:
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77 | * 1) The use of this style of critical section is targetted at C based implementations.
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78 | * 2) These critical sections can be nested.
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79 | * 3) The interrupt enable state on entry to the first critical section (of a nested set, or single
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80 | * section) will be preserved on exit from the section.
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81 | * 4) This implementation will currently only work on code running in privileged mode.
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82 | */
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83 | void core_util_critical_section_exit(void);
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84 |
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85 | /**
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86 | * Determine if we are currently in a critical section
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87 | *
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88 | * @return true if in a critical section, false otherwise.
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89 | */
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90 | bool core_util_in_critical_section(void);
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91 |
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92 | /**
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93 | * Atomic compare and set. It compares the contents of a memory location to a
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94 | * given value and, only if they are the same, modifies the contents of that
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95 | * memory location to a given new value. This is done as a single atomic
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96 | * operation. The atomicity guarantees that the new value is calculated based on
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97 | * up-to-date information; if the value had been updated by another thread in
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98 | * the meantime, the write would fail due to a mismatched expectedCurrentValue.
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99 | *
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100 | * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
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101 | * you to the article on compare-and swap].
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102 | *
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103 | * @param ptr The target memory location.
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104 | * @param[in,out] expectedCurrentValue A pointer to some location holding the
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105 | * expected current value of the data being set atomically.
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106 | * The computed 'desiredValue' should be a function of this current value.
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107 | * @note: This is an in-out parameter. In the
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108 | * failure case of atomic_cas (where the
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109 | * destination isn't set), the pointee of expectedCurrentValue is
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110 | * updated with the current value.
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111 | * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'.
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112 | *
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113 | * @return true if the memory location was atomically
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114 | * updated with the desired value (after verifying
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115 | * that it contained the expectedCurrentValue),
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116 | * false otherwise. In the failure case,
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117 | * exepctedCurrentValue is updated with the new
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118 | * value of the target memory location.
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119 | *
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120 | * pseudocode:
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121 | * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
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122 | * if *p != *old {
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123 | * *old = *p
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124 | * return false
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125 | * }
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126 | * *p = new
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127 | * return true
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128 | * }
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129 | *
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130 | * @note: In the failure case (where the destination isn't set), the value
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131 | * pointed to by expectedCurrentValue is instead updated with the current value.
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132 | * This property helps writing concise code for the following incr:
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133 | *
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134 | * function incr(p : pointer to int, a : int) returns int {
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135 | * done = false
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136 | * value = *p // This fetch operation need not be atomic.
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137 | * while not done {
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138 | * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
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139 | * }
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140 | * return value + a
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141 | * }
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142 | *
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143 | * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
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144 | * always succeeds if the current value is expected, as per the pseudocode
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145 | * above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
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146 | */
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147 | bool core_util_atomic_cas_u8(volatile uint8_t *ptr, uint8_t *expectedCurrentValue, uint8_t desiredValue);
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148 |
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149 | /**
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150 | * Atomic compare and set. It compares the contents of a memory location to a
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151 | * given value and, only if they are the same, modifies the contents of that
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152 | * memory location to a given new value. This is done as a single atomic
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153 | * operation. The atomicity guarantees that the new value is calculated based on
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154 | * up-to-date information; if the value had been updated by another thread in
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155 | * the meantime, the write would fail due to a mismatched expectedCurrentValue.
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156 | *
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157 | * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
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158 | * you to the article on compare-and swap].
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159 | *
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160 | * @param ptr The target memory location.
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161 | * @param[in,out] expectedCurrentValue A pointer to some location holding the
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162 | * expected current value of the data being set atomically.
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163 | * The computed 'desiredValue' should be a function of this current value.
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164 | * @note: This is an in-out parameter. In the
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165 | * failure case of atomic_cas (where the
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166 | * destination isn't set), the pointee of expectedCurrentValue is
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167 | * updated with the current value.
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168 | * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'.
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169 | *
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170 | * @return true if the memory location was atomically
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171 | * updated with the desired value (after verifying
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172 | * that it contained the expectedCurrentValue),
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173 | * false otherwise. In the failure case,
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174 | * exepctedCurrentValue is updated with the new
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175 | * value of the target memory location.
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176 | *
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177 | * pseudocode:
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178 | * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
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179 | * if *p != *old {
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180 | * *old = *p
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181 | * return false
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182 | * }
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183 | * *p = new
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184 | * return true
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185 | * }
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186 | *
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187 | * @note: In the failure case (where the destination isn't set), the value
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188 | * pointed to by expectedCurrentValue is instead updated with the current value.
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189 | * This property helps writing concise code for the following incr:
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190 | *
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191 | * function incr(p : pointer to int, a : int) returns int {
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192 | * done = false
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193 | * value = *p // This fetch operation need not be atomic.
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194 | * while not done {
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195 | * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
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196 | * }
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197 | * return value + a
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198 | * }
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199 | *
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200 | * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
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201 | * always succeeds if the current value is expected, as per the pseudocode
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202 | * above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
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203 | */
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204 | bool core_util_atomic_cas_u16(volatile uint16_t *ptr, uint16_t *expectedCurrentValue, uint16_t desiredValue);
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205 |
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206 | /**
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207 | * Atomic compare and set. It compares the contents of a memory location to a
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208 | * given value and, only if they are the same, modifies the contents of that
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209 | * memory location to a given new value. This is done as a single atomic
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210 | * operation. The atomicity guarantees that the new value is calculated based on
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211 | * up-to-date information; if the value had been updated by another thread in
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212 | * the meantime, the write would fail due to a mismatched expectedCurrentValue.
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213 | *
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214 | * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
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215 | * you to the article on compare-and swap].
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216 | *
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217 | * @param ptr The target memory location.
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218 | * @param[in,out] expectedCurrentValue A pointer to some location holding the
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219 | * expected current value of the data being set atomically.
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220 | * The computed 'desiredValue' should be a function of this current value.
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221 | * @note: This is an in-out parameter. In the
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222 | * failure case of atomic_cas (where the
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223 | * destination isn't set), the pointee of expectedCurrentValue is
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224 | * updated with the current value.
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225 | * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'.
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226 | *
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227 | * @return true if the memory location was atomically
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228 | * updated with the desired value (after verifying
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229 | * that it contained the expectedCurrentValue),
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230 | * false otherwise. In the failure case,
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231 | * exepctedCurrentValue is updated with the new
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232 | * value of the target memory location.
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233 | *
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234 | * pseudocode:
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235 | * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
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236 | * if *p != *old {
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237 | * *old = *p
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238 | * return false
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239 | * }
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240 | * *p = new
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241 | * return true
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242 | * }
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243 | *
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244 | * @note: In the failure case (where the destination isn't set), the value
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245 | * pointed to by expectedCurrentValue is instead updated with the current value.
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246 | * This property helps writing concise code for the following incr:
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247 | *
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248 | * function incr(p : pointer to int, a : int) returns int {
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249 | * done = false
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250 | * value = *p // This fetch operation need not be atomic.
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251 | * while not done {
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252 | * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
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253 | * }
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254 | * return value + a
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255 | *
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256 | * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
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257 | * always succeeds if the current value is expected, as per the pseudocode
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258 | * above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
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259 | * }
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260 | */
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261 | bool core_util_atomic_cas_u32(volatile uint32_t *ptr, uint32_t *expectedCurrentValue, uint32_t desiredValue);
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262 |
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263 | /**
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264 | * Atomic compare and set. It compares the contents of a memory location to a
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265 | * given value and, only if they are the same, modifies the contents of that
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266 | * memory location to a given new value. This is done as a single atomic
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267 | * operation. The atomicity guarantees that the new value is calculated based on
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268 | * up-to-date information; if the value had been updated by another thread in
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269 | * the meantime, the write would fail due to a mismatched expectedCurrentValue.
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270 | *
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271 | * Refer to https://en.wikipedia.org/wiki/Compare-and-set [which may redirect
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272 | * you to the article on compare-and swap].
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273 | *
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274 | * @param ptr The target memory location.
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275 | * @param[in,out] expectedCurrentValue A pointer to some location holding the
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276 | * expected current value of the data being set atomically.
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277 | * The computed 'desiredValue' should be a function of this current value.
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278 | * @note: This is an in-out parameter. In the
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279 | * failure case of atomic_cas (where the
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280 | * destination isn't set), the pointee of expectedCurrentValue is
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281 | * updated with the current value.
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282 | * @param[in] desiredValue The new value computed based on '*expectedCurrentValue'.
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283 | *
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284 | * @return true if the memory location was atomically
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285 | * updated with the desired value (after verifying
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286 | * that it contained the expectedCurrentValue),
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287 | * false otherwise. In the failure case,
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288 | * exepctedCurrentValue is updated with the new
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289 | * value of the target memory location.
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290 | *
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291 | * pseudocode:
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292 | * function cas(p : pointer to int, old : pointer to int, new : int) returns bool {
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293 | * if *p != *old {
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294 | * *old = *p
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295 | * return false
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296 | * }
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297 | * *p = new
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298 | * return true
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299 | * }
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300 | *
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301 | * @note: In the failure case (where the destination isn't set), the value
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302 | * pointed to by expectedCurrentValue is instead updated with the current value.
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303 | * This property helps writing concise code for the following incr:
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304 | *
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305 | * function incr(p : pointer to int, a : int) returns int {
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306 | * done = false
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307 | * value = *p // This fetch operation need not be atomic.
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308 | * while not done {
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309 | * done = atomic_cas(p, &value, value + a) // *value gets updated automatically until success
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310 | * }
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311 | * return value + a
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312 | * }
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313 | *
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314 | * @note: This corresponds to the C11 "atomic_compare_exchange_strong" - it
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315 | * always succeeds if the current value is expected, as per the pseudocode
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316 | * above; it will not spuriously fail as "atomic_compare_exchange_weak" may.
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317 | */
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318 | bool core_util_atomic_cas_ptr(void *volatile *ptr, void **expectedCurrentValue, void *desiredValue);
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319 |
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320 | /**
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321 | * Atomic increment.
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322 | * @param valuePtr Target memory location being incremented.
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323 | * @param delta The amount being incremented.
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324 | * @return The new incremented value.
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325 | */
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326 | uint8_t core_util_atomic_incr_u8(volatile uint8_t *valuePtr, uint8_t delta);
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327 |
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328 | /**
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329 | * Atomic increment.
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330 | * @param valuePtr Target memory location being incremented.
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331 | * @param delta The amount being incremented.
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332 | * @return The new incremented value.
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333 | */
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334 | uint16_t core_util_atomic_incr_u16(volatile uint16_t *valuePtr, uint16_t delta);
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335 |
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336 | /**
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337 | * Atomic increment.
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338 | * @param valuePtr Target memory location being incremented.
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339 | * @param delta The amount being incremented.
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340 | * @return The new incremented value.
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341 | */
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342 | uint32_t core_util_atomic_incr_u32(volatile uint32_t *valuePtr, uint32_t delta);
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343 |
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344 | /**
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345 | * Atomic increment.
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346 | * @param valuePtr Target memory location being incremented.
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347 | * @param delta The amount being incremented in bytes.
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348 | * @return The new incremented value.
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349 | *
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350 | * @note The type of the pointer argument is not taken into account
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351 | * and the pointer is incremented by bytes.
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352 | */
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353 | void *core_util_atomic_incr_ptr(void *volatile *valuePtr, ptrdiff_t delta);
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354 |
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355 | /**
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356 | * Atomic decrement.
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357 | * @param valuePtr Target memory location being decremented.
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358 | * @param delta The amount being decremented.
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359 | * @return The new decremented value.
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360 | */
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361 | uint8_t core_util_atomic_decr_u8(volatile uint8_t *valuePtr, uint8_t delta);
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362 |
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363 | /**
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364 | * Atomic decrement.
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365 | * @param valuePtr Target memory location being decremented.
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366 | * @param delta The amount being decremented.
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367 | * @return The new decremented value.
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368 | */
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369 | uint16_t core_util_atomic_decr_u16(volatile uint16_t *valuePtr, uint16_t delta);
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370 |
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371 | /**
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372 | * Atomic decrement.
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373 | * @param valuePtr Target memory location being decremented.
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374 | * @param delta The amount being decremented.
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375 | * @return The new decremented value.
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376 | */
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377 | uint32_t core_util_atomic_decr_u32(volatile uint32_t *valuePtr, uint32_t delta);
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378 |
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379 | /**
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380 | * Atomic decrement.
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381 | * @param valuePtr Target memory location being decremented.
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382 | * @param delta The amount being decremented in bytes.
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383 | * @return The new decremented value.
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384 | *
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385 | * @note The type of the pointer argument is not taken into account
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386 | * and the pointer is decremented by bytes
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387 | */
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388 | void *core_util_atomic_decr_ptr(void *volatile *valuePtr, ptrdiff_t delta);
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389 |
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390 | #ifdef __cplusplus
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391 | } // extern "C"
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392 | #endif
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393 | /**@}*/
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394 |
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395 | /**@}*/
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396 |
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397 | #endif // __MBED_UTIL_CRITICAL_H__
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398 |
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399 |
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400 |
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