root / arduino-1.0 / hardware / arduino / firmwares / arduino-usbserial / Lib / LightweightRingBuff.h @ 58d82c77
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1 | 58d82c77 | Tom Mullins | /*
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2 | LUFA Library
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3 | Copyright (C) Dean Camera, 2010.
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4 |
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5 | dean [at] fourwalledcubicle [dot] com
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6 | www.fourwalledcubicle.com
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7 | */
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8 | |||
9 | /*
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10 | Copyright 2010 Dean Camera (dean [at] fourwalledcubicle [dot] com)
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11 | |||
12 | Permission to use, copy, modify, distribute, and sell this
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13 | software and its documentation for any purpose is hereby granted
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14 | without fee, provided that the above copyright notice appear in
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15 | all copies and that both that the copyright notice and this
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16 | permission notice and warranty disclaimer appear in supporting
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17 | documentation, and that the name of the author not be used in
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18 | advertising or publicity pertaining to distribution of the
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19 | software without specific, written prior permission.
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20 | |||
21 | The author disclaim all warranties with regard to this
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22 | software, including all implied warranties of merchantability
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23 | and fitness. In no event shall the author be liable for any
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24 | special, indirect or consequential damages or any damages
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25 | whatsoever resulting from loss of use, data or profits, whether
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26 | in an action of contract, negligence or other tortious action,
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27 | arising out of or in connection with the use or performance of
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28 | this software.
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29 | */
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30 | |||
31 | /** \file
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32 | *
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33 | * Ultra lightweight ring buffer, for fast insertion/deletion.
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34 | */
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35 | |||
36 | #ifndef _ULW_RING_BUFF_H_
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37 | #define _ULW_RING_BUFF_H_
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38 | |||
39 | /* Includes: */
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40 | #include <util/atomic.h> |
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41 | |||
42 | #include <stdint.h> |
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43 | #include <stdbool.h> |
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44 | |||
45 | /* Defines: */
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46 | /** Size of each ring buffer, in data elements - must be between 1 and 255. */
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47 | #define BUFFER_SIZE 128 |
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48 | |||
49 | /** Maximum number of data elements to buffer before forcing a flush.
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50 | * Must be less than BUFFER_SIZE
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51 | */
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52 | #define BUFFER_NEARLY_FULL 96 |
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53 | |||
54 | /** Type of data to store into the buffer. */
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55 | #define RingBuff_Data_t uint8_t
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56 | |||
57 | /** Datatype which may be used to store the count of data stored in a buffer, retrieved
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58 | * via a call to \ref RingBuffer_GetCount().
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59 | */
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60 | #if (BUFFER_SIZE <= 0xFF) |
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61 | #define RingBuff_Count_t uint8_t
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62 | #else
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63 | #define RingBuff_Count_t uint16_t
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64 | #endif
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65 | |||
66 | /* Type Defines: */
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67 | /** Type define for a new ring buffer object. Buffers should be initialized via a call to
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68 | * \ref RingBuffer_InitBuffer() before use.
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69 | */
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70 | typedef struct |
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71 | { |
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72 | RingBuff_Data_t Buffer[BUFFER_SIZE]; /**< Internal ring buffer data, referenced by the buffer pointers. */
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73 | RingBuff_Data_t* In; /**< Current storage location in the circular buffer */
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74 | RingBuff_Data_t* Out; /**< Current retrieval location in the circular buffer */
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75 | RingBuff_Count_t Count; |
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76 | } RingBuff_t; |
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77 | |||
78 | /* Inline Functions: */
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79 | /** Initializes a ring buffer ready for use. Buffers must be initialized via this function
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80 | * before any operations are called upon them. Already initialized buffers may be reset
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81 | * by re-initializing them using this function.
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82 | *
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83 | * \param[out] Buffer Pointer to a ring buffer structure to initialize
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84 | */
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85 | static inline void RingBuffer_InitBuffer(RingBuff_t* const Buffer) |
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86 | { |
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87 | ATOMIC_BLOCK(ATOMIC_RESTORESTATE) |
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88 | { |
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89 | Buffer->In = Buffer->Buffer; |
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90 | Buffer->Out = Buffer->Buffer; |
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91 | } |
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92 | } |
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93 | |||
94 | /** Retrieves the minimum number of bytes stored in a particular buffer. This value is computed
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95 | * by entering an atomic lock on the buffer while the IN and OUT locations are fetched, so that
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96 | * the buffer cannot be modified while the computation takes place. This value should be cached
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97 | * when reading out the contents of the buffer, so that as small a time as possible is spent
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98 | * in an atomic lock.
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99 | *
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100 | * \note The value returned by this function is guaranteed to only be the minimum number of bytes
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101 | * stored in the given buffer; this value may change as other threads write new data and so
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102 | * the returned number should be used only to determine how many successive reads may safely
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103 | * be performed on the buffer.
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104 | *
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105 | * \param[in] Buffer Pointer to a ring buffer structure whose count is to be computed
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106 | */
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107 | static inline RingBuff_Count_t RingBuffer_GetCount(RingBuff_t* const Buffer) |
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108 | { |
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109 | RingBuff_Count_t Count; |
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110 | |||
111 | ATOMIC_BLOCK(ATOMIC_RESTORESTATE) |
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112 | { |
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113 | Count = Buffer->Count; |
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114 | } |
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115 | |||
116 | return Count;
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117 | } |
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118 | |||
119 | /** Atomically determines if the specified ring buffer contains any free space. This should
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120 | * be tested before storing data to the buffer, to ensure that no data is lost due to a
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121 | * buffer overrun.
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122 | *
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123 | * \param[in,out] Buffer Pointer to a ring buffer structure to insert into
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124 | *
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125 | * \return Boolean true if the buffer contains no free space, false otherwise
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126 | */
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127 | static inline bool RingBuffer_IsFull(RingBuff_t* const Buffer) |
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128 | { |
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129 | return (RingBuffer_GetCount(Buffer) == BUFFER_SIZE);
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130 | } |
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131 | |||
132 | /** Atomically determines if the specified ring buffer contains any data. This should
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133 | * be tested before removing data from the buffer, to ensure that the buffer does not
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134 | * underflow.
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135 | *
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136 | * If the data is to be removed in a loop, store the total number of bytes stored in the
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137 | * buffer (via a call to the \ref RingBuffer_GetCount() function) in a temporary variable
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138 | * to reduce the time spent in atomicity locks.
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139 | *
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140 | * \param[in,out] Buffer Pointer to a ring buffer structure to insert into
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141 | *
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142 | * \return Boolean true if the buffer contains no free space, false otherwise
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143 | */
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144 | static inline bool RingBuffer_IsEmpty(RingBuff_t* const Buffer) |
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145 | { |
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146 | return (RingBuffer_GetCount(Buffer) == 0); |
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147 | } |
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148 | |||
149 | /** Inserts an element into the ring buffer.
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150 | *
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151 | * \note Only one execution thread (main program thread or an ISR) may insert into a single buffer
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152 | * otherwise data corruption may occur. Insertion and removal may occur from different execution
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153 | * threads.
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154 | *
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155 | * \param[in,out] Buffer Pointer to a ring buffer structure to insert into
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156 | * \param[in] Data Data element to insert into the buffer
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157 | */
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158 | static inline void RingBuffer_Insert(RingBuff_t* const Buffer, |
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159 | const RingBuff_Data_t Data)
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160 | { |
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161 | *Buffer->In = Data; |
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162 | |||
163 | if (++Buffer->In == &Buffer->Buffer[BUFFER_SIZE])
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164 | Buffer->In = Buffer->Buffer; |
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165 | |||
166 | ATOMIC_BLOCK(ATOMIC_RESTORESTATE) |
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167 | { |
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168 | Buffer->Count++; |
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169 | } |
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170 | } |
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171 | |||
172 | /** Removes an element from the ring buffer.
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173 | *
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174 | * \note Only one execution thread (main program thread or an ISR) may remove from a single buffer
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175 | * otherwise data corruption may occur. Insertion and removal may occur from different execution
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176 | * threads.
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177 | *
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178 | * \param[in,out] Buffer Pointer to a ring buffer structure to retrieve from
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179 | *
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180 | * \return Next data element stored in the buffer
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181 | */
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182 | static inline RingBuff_Data_t RingBuffer_Remove(RingBuff_t* const Buffer) |
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183 | { |
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184 | RingBuff_Data_t Data = *Buffer->Out; |
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185 | |||
186 | if (++Buffer->Out == &Buffer->Buffer[BUFFER_SIZE])
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187 | Buffer->Out = Buffer->Buffer; |
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188 | |||
189 | ATOMIC_BLOCK(ATOMIC_RESTORESTATE) |
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190 | { |
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191 | Buffer->Count--; |
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192 | } |
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193 | |||
194 | return Data;
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195 | } |
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196 | |||
197 | #endif
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