memcpy_P函數AVR？

Question

void * memcpy_P（void * dest，PGM_VOID_P src，size_t n）

有人可以告訴我在avr libc庫中實現上述函數的位置嗎？

我似乎只能在幾個頭文件中找到函數的定義，而不是實際的實現。

我想這樣做的原因是因爲目前我正在AVRAtmega128rfa1上進行性能測試，我還需要查看該函數的AVR彙編代碼，看看它需要多長時間才能執行。

謝謝。

Answer 1

在AVR-的libc-1.8.0，該函數中定義AVR-的libc-1.8.0 /的libc/pmstring/memcpy_P.S

/* Copyright (c) 2002, 2005, 2006, 2007 Marek Michalkiewicz 
    All rights reserved. 

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    modification, are permitted provided that the following conditions are met: 

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    contributors may be used to endorse or promote products derived 
    from this software without specific prior written permission. 

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
    ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
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    CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
    ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
    POSSIBILITY OF SUCH DAMAGE. */ 

/* $Id: memcpy_P.S 2191 2010-11-05 13:45:57Z arcanum $ */ 

/** \file */ 
/** \ingroup avr_pgmspace 
    \fn void *memcpy_P(void *dest, PGM_VOID_P src, size_t n) 

    The memcpy_P() function is similar to memcpy(), except the src string 
    resides in program space. 

    \returns The memcpy_P() function returns a pointer to dest. */ 


#if !defined(__AVR_TINY__) 

#if !defined(__DOXYGEN__) 

#include "macros.inc" 

#define dest_hi r25 
#define dest_lo r24 
#define src_hi r23 
#define src_lo r22 
#define len_hi r21 
#define len_lo r20 

    ASSEMBLY_CLIB_SECTION 
    .global _U(memcpy_P) 
    .type _U(memcpy_P), @function 
_U(memcpy_P): 
    X_movw ZL, src_lo 
    X_movw XL, dest_lo 
#if OPTIMIZE_SPEED 
; 17 words, (14 + len * 9 - (len & 1)) cycles 
    sbrs len_lo, 0 
    rjmp .L_memcpy_P_start 
    rjmp .L_memcpy_P_odd 
.L_memcpy_P_loop: 
    X_lpm r0, Z+ 
    st X+, r0 
.L_memcpy_P_odd: 
    X_lpm r0, Z+ 
    st X+, r0 
.L_memcpy_P_start: 
    subi len_lo, lo8(2) 
    sbci len_hi, hi8(2) 
#else 
; 12 words, (13 + len * 11) cycles 
    rjmp .L_memcpy_P_start 
.L_memcpy_P_loop: 
    X_lpm r0, Z+ 
    st X+, r0 
.L_memcpy_P_start: 
    subi len_lo, lo8(1) 
    sbci len_hi, hi8(1) 
#endif 
    brcc .L_memcpy_P_loop 
; return dest (unchanged) 
    ret 
.L_memcpy_P_end: 
    .size _U(memcpy_P), .L_memcpy_P_end - _U(memcpy_P) 

#endif /* not __DOXYGEN__ */ 

#endif /* !defined(__AVR_TINY__) */