Yasushi TAUCHI / Mbed 2 deprecated giken9_HTMLServer_Sample

ソースの整理中ですが、利用はできます。

Dependencies:   EthernetInterface HttpServer TextLCD mbed-rpc mbed-rtos mbed Socket lwip-eth lwip-sys lwip

EthernetInterface/lwip-sys/arch/checksum.c@0:7766f6712673, 2014-03-12 (annotated)

Committer:
yueee_yt
Date:
Wed Mar 12 04:19:54 2014 +0000
Revision:
0:7766f6712673
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Who changed what in which revision?

UserRevisionLine numberNew contents of line
yueee_yt 0:7766f6712673 1 /* Copyright (C) 2013 - Adam Green (https://github.com/adamgreen)
yueee_yt 0:7766f6712673 2
yueee_yt 0:7766f6712673 3 Licensed under the Apache License, Version 2.0 (the "License");
yueee_yt 0:7766f6712673 4 you may not use this file except in compliance with the License.
yueee_yt 0:7766f6712673 5 You may obtain a copy of the License at
yueee_yt 0:7766f6712673 6
yueee_yt 0:7766f6712673 7 http://www.apache.org/licenses/LICENSE-2.0
yueee_yt 0:7766f6712673 8
yueee_yt 0:7766f6712673 9 Unless required by applicable law or agreed to in writing, software
yueee_yt 0:7766f6712673 10 distributed under the License is distributed on an "AS IS" BASIS,
yueee_yt 0:7766f6712673 11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
yueee_yt 0:7766f6712673 12 See the License for the specific language governing permissions and
yueee_yt 0:7766f6712673 13 limitations under the License.
yueee_yt 0:7766f6712673 14 */
yueee_yt 0:7766f6712673 15 #if defined(TOOLCHAIN_GCC) && defined(__thumb2__)
yueee_yt 0:7766f6712673 16
yueee_yt 0:7766f6712673 17
yueee_yt 0:7766f6712673 18 /* This is a hand written Thumb-2 assembly language version of the
yueee_yt 0:7766f6712673 19 algorithm 3 version of lwip_standard_chksum in lwIP's inet_chksum.c. It
yueee_yt 0:7766f6712673 20 performs the checksumming 32-bits at a time and even unrolls the loop to
yueee_yt 0:7766f6712673 21 perform two of these 32-bit adds per loop iteration.
yueee_yt 0:7766f6712673 22
yueee_yt 0:7766f6712673 23 Returns:
yueee_yt 0:7766f6712673 24 16-bit 1's complement summation (not inversed).
yueee_yt 0:7766f6712673 25
yueee_yt 0:7766f6712673 26 NOTE: This function does return a uint16_t from the assembly language code
yueee_yt 0:7766f6712673 27 but is marked as void so that GCC doesn't issue warning because it
yueee_yt 0:7766f6712673 28 doesn't know about this low level return.
yueee_yt 0:7766f6712673 29 */
yueee_yt 0:7766f6712673 30 __attribute__((naked)) void /*uint16_t*/ thumb2_checksum(const void* pData, int length)
yueee_yt 0:7766f6712673 31 {
yueee_yt 0:7766f6712673 32 __asm (
yueee_yt 0:7766f6712673 33 ".syntax unified\n"
yueee_yt 0:7766f6712673 34 ".thumb\n"
yueee_yt 0:7766f6712673 35
yueee_yt 0:7766f6712673 36 // Push non-volatile registers we use on stack. Push link register too to
yueee_yt 0:7766f6712673 37 // keep stack 8-byte aligned and allow single pop to restore and return.
yueee_yt 0:7766f6712673 38 " push {r4, lr}\n"
yueee_yt 0:7766f6712673 39 // Initialize sum, r2, to 0.
yueee_yt 0:7766f6712673 40 " movs r2, #0\n"
yueee_yt 0:7766f6712673 41 // Remember whether pData was at odd address in r3. This is used later to
yueee_yt 0:7766f6712673 42 // know if it needs to swap the result since the summation will be done at
yueee_yt 0:7766f6712673 43 // an offset of 1, rather than 0.
yueee_yt 0:7766f6712673 44 " ands r3, r0, #1\n"
yueee_yt 0:7766f6712673 45 // Need to 2-byte align? If not skip ahead.
yueee_yt 0:7766f6712673 46 " beq 1$\n"
yueee_yt 0:7766f6712673 47 // We can return if there are no bytes to sum.
yueee_yt 0:7766f6712673 48 " cbz r1, 9$\n"
yueee_yt 0:7766f6712673 49
yueee_yt 0:7766f6712673 50 // 2-byte align.
yueee_yt 0:7766f6712673 51 // Place the first data byte in odd summation location since it needs to be
yueee_yt 0:7766f6712673 52 // swapped later. It's ok to overwrite r2 here as it only had a value of 0
yueee_yt 0:7766f6712673 53 // up until now. Advance r0 pointer and decrement r1 length as we go.
yueee_yt 0:7766f6712673 54 " ldrb r2, [r0], #1\n"
yueee_yt 0:7766f6712673 55 " lsls r2, r2, #8\n"
yueee_yt 0:7766f6712673 56 " subs r1, r1, #1\n"
yueee_yt 0:7766f6712673 57
yueee_yt 0:7766f6712673 58 // Need to 4-byte align? If not skip ahead.
yueee_yt 0:7766f6712673 59 "1$:\n"
yueee_yt 0:7766f6712673 60 " ands r4, r0, #3\n"
yueee_yt 0:7766f6712673 61 " beq 2$\n"
yueee_yt 0:7766f6712673 62 // Have more than 1 byte left to align? If not skip ahead to take care of
yueee_yt 0:7766f6712673 63 // trailing byte.
yueee_yt 0:7766f6712673 64 " cmp r1, #2\n"
yueee_yt 0:7766f6712673 65 " blt 7$\n"
yueee_yt 0:7766f6712673 66
yueee_yt 0:7766f6712673 67 // 4-byte align.
yueee_yt 0:7766f6712673 68 " ldrh r4, [r0], #2\n"
yueee_yt 0:7766f6712673 69 " adds r2, r2, r4\n"
yueee_yt 0:7766f6712673 70 " subs r1, r1, #2\n"
yueee_yt 0:7766f6712673 71
yueee_yt 0:7766f6712673 72 // Main summing loop which sums up data 2 words at a time.
yueee_yt 0:7766f6712673 73 // Make sure that we have more than 7 bytes left to sum.
yueee_yt 0:7766f6712673 74 "2$:\n"
yueee_yt 0:7766f6712673 75 " cmp r1, #8\n"
yueee_yt 0:7766f6712673 76 " blt 3$\n"
yueee_yt 0:7766f6712673 77 // Sum next two words. Applying previous upper 16-bit carry to
yueee_yt 0:7766f6712673 78 // lower 16-bits.
yueee_yt 0:7766f6712673 79 " ldr r4, [r0], #4\n"
yueee_yt 0:7766f6712673 80 " adds r2, r4\n"
yueee_yt 0:7766f6712673 81 " adc r2, r2, #0\n"
yueee_yt 0:7766f6712673 82 " ldr r4, [r0], #4\n"
yueee_yt 0:7766f6712673 83 " adds r2, r4\n"
yueee_yt 0:7766f6712673 84 " adc r2, r2, #0\n"
yueee_yt 0:7766f6712673 85 " subs r1, r1, #8\n"
yueee_yt 0:7766f6712673 86 " b 2$\n"
yueee_yt 0:7766f6712673 87
yueee_yt 0:7766f6712673 88 // Sum up any remaining half-words.
yueee_yt 0:7766f6712673 89 "3$:\n"
yueee_yt 0:7766f6712673 90 // Make sure that we have more than 1 byte left to sum.
yueee_yt 0:7766f6712673 91 " cmp r1, #2\n"
yueee_yt 0:7766f6712673 92 " blt 7$\n"
yueee_yt 0:7766f6712673 93 // Sum up next half word, continue to apply carry.
yueee_yt 0:7766f6712673 94 " ldrh r4, [r0], #2\n"
yueee_yt 0:7766f6712673 95 " adds r2, r4\n"
yueee_yt 0:7766f6712673 96 " adc r2, r2, #0\n"
yueee_yt 0:7766f6712673 97 " subs r1, r1, #2\n"
yueee_yt 0:7766f6712673 98 " b 3$\n"
yueee_yt 0:7766f6712673 99
yueee_yt 0:7766f6712673 100 // Handle trailing byte, if it exists
yueee_yt 0:7766f6712673 101 "7$:\n"
yueee_yt 0:7766f6712673 102 " cbz r1, 8$\n"
yueee_yt 0:7766f6712673 103 " ldrb r4, [r0]\n"
yueee_yt 0:7766f6712673 104 " adds r2, r4\n"
yueee_yt 0:7766f6712673 105 " adc r2, r2, #0\n"
yueee_yt 0:7766f6712673 106
yueee_yt 0:7766f6712673 107 // Fold 32-bit checksum into 16-bit checksum.
yueee_yt 0:7766f6712673 108 "8$:\n"
yueee_yt 0:7766f6712673 109 " ubfx r4, r2, #16, #16\n"
yueee_yt 0:7766f6712673 110 " ubfx r2, r2, #0, #16\n"
yueee_yt 0:7766f6712673 111 " adds r2, r4\n"
yueee_yt 0:7766f6712673 112 " ubfx r4, r2, #16, #16\n"
yueee_yt 0:7766f6712673 113 " ubfx r2, r2, #0, #16\n"
yueee_yt 0:7766f6712673 114 " adds r2, r4\n"
yueee_yt 0:7766f6712673 115
yueee_yt 0:7766f6712673 116 // Swap bytes if started at odd address
yueee_yt 0:7766f6712673 117 " cbz r3, 9$\n"
yueee_yt 0:7766f6712673 118 " rev16 r2, r2\n"
yueee_yt 0:7766f6712673 119
yueee_yt 0:7766f6712673 120 // Return final sum.
yueee_yt 0:7766f6712673 121 "9$: mov r0, r2\n"
yueee_yt 0:7766f6712673 122 " pop {r4, pc}\n"
yueee_yt 0:7766f6712673 123 );
yueee_yt 0:7766f6712673 124 }
yueee_yt 0:7766f6712673 125
yueee_yt 0:7766f6712673 126 #endif