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Dependencies:   F7_Ethernet WebSocketClient mbed mcp3008

Fork of Nucleo_F746ZG_Ethernet by Dieter Graef

F7_Ethernet/lwip-sys/arch/checksum.c@0:f9b6112278fe, 2016-06-18 (annotated)

Committer:
DieterGraef
Date:
Sat Jun 18 10:49:12 2016 +0000
Revision:
0:f9b6112278fe
Ethernet for the NUCLEO STM32F746 Board Testprogram uses DHCP and NTP to set the clock

Who changed what in which revision?

UserRevisionLine numberNew contents of line
DieterGraef 0:f9b6112278fe 1 /* Copyright (C) 2013 - Adam Green (https://github.com/adamgreen)
DieterGraef 0:f9b6112278fe 2
DieterGraef 0:f9b6112278fe 3 Licensed under the Apache License, Version 2.0 (the "License");
DieterGraef 0:f9b6112278fe 4 you may not use this file except in compliance with the License.
DieterGraef 0:f9b6112278fe 5 You may obtain a copy of the License at
DieterGraef 0:f9b6112278fe 6
DieterGraef 0:f9b6112278fe 7 http://www.apache.org/licenses/LICENSE-2.0
DieterGraef 0:f9b6112278fe 8
DieterGraef 0:f9b6112278fe 9 Unless required by applicable law or agreed to in writing, software
DieterGraef 0:f9b6112278fe 10 distributed under the License is distributed on an "AS IS" BASIS,
DieterGraef 0:f9b6112278fe 11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
DieterGraef 0:f9b6112278fe 12 See the License for the specific language governing permissions and
DieterGraef 0:f9b6112278fe 13 limitations under the License.
DieterGraef 0:f9b6112278fe 14 */
DieterGraef 0:f9b6112278fe 15 #if defined(TOOLCHAIN_GCC) && defined(__thumb2__)
DieterGraef 0:f9b6112278fe 16
DieterGraef 0:f9b6112278fe 17
DieterGraef 0:f9b6112278fe 18 /* This is a hand written Thumb-2 assembly language version of the
DieterGraef 0:f9b6112278fe 19 algorithm 3 version of lwip_standard_chksum in lwIP's inet_chksum.c. It
DieterGraef 0:f9b6112278fe 20 performs the checksumming 32-bits at a time and even unrolls the loop to
DieterGraef 0:f9b6112278fe 21 perform two of these 32-bit adds per loop iteration.
DieterGraef 0:f9b6112278fe 22
DieterGraef 0:f9b6112278fe 23 Returns:
DieterGraef 0:f9b6112278fe 24 16-bit 1's complement summation (not inversed).
DieterGraef 0:f9b6112278fe 25
DieterGraef 0:f9b6112278fe 26 NOTE: This function does return a uint16_t from the assembly language code
DieterGraef 0:f9b6112278fe 27 but is marked as void so that GCC doesn't issue warning because it
DieterGraef 0:f9b6112278fe 28 doesn't know about this low level return.
DieterGraef 0:f9b6112278fe 29 */
DieterGraef 0:f9b6112278fe 30 __attribute__((naked)) void /*uint16_t*/ thumb2_checksum(const void* pData, int length)
DieterGraef 0:f9b6112278fe 31 {
DieterGraef 0:f9b6112278fe 32 __asm (
DieterGraef 0:f9b6112278fe 33 ".syntax unified\n"
DieterGraef 0:f9b6112278fe 34 ".thumb\n"
DieterGraef 0:f9b6112278fe 35
DieterGraef 0:f9b6112278fe 36 // Push non-volatile registers we use on stack. Push link register too to
DieterGraef 0:f9b6112278fe 37 // keep stack 8-byte aligned and allow single pop to restore and return.
DieterGraef 0:f9b6112278fe 38 " push {r4, lr}\n"
DieterGraef 0:f9b6112278fe 39 // Initialize sum, r2, to 0.
DieterGraef 0:f9b6112278fe 40 " movs r2, #0\n"
DieterGraef 0:f9b6112278fe 41 // Remember whether pData was at odd address in r3. This is used later to
DieterGraef 0:f9b6112278fe 42 // know if it needs to swap the result since the summation will be done at
DieterGraef 0:f9b6112278fe 43 // an offset of 1, rather than 0.
DieterGraef 0:f9b6112278fe 44 " ands r3, r0, #1\n"
DieterGraef 0:f9b6112278fe 45 // Need to 2-byte align? If not skip ahead.
DieterGraef 0:f9b6112278fe 46 " beq 1$\n"
DieterGraef 0:f9b6112278fe 47 // We can return if there are no bytes to sum.
DieterGraef 0:f9b6112278fe 48 " cbz r1, 9$\n"
DieterGraef 0:f9b6112278fe 49
DieterGraef 0:f9b6112278fe 50 // 2-byte align.
DieterGraef 0:f9b6112278fe 51 // Place the first data byte in odd summation location since it needs to be
DieterGraef 0:f9b6112278fe 52 // swapped later. It's ok to overwrite r2 here as it only had a value of 0
DieterGraef 0:f9b6112278fe 53 // up until now. Advance r0 pointer and decrement r1 length as we go.
DieterGraef 0:f9b6112278fe 54 " ldrb r2, [r0], #1\n"
DieterGraef 0:f9b6112278fe 55 " lsls r2, r2, #8\n"
DieterGraef 0:f9b6112278fe 56 " subs r1, r1, #1\n"
DieterGraef 0:f9b6112278fe 57
DieterGraef 0:f9b6112278fe 58 // Need to 4-byte align? If not skip ahead.
DieterGraef 0:f9b6112278fe 59 "1$:\n"
DieterGraef 0:f9b6112278fe 60 " ands r4, r0, #3\n"
DieterGraef 0:f9b6112278fe 61 " beq 2$\n"
DieterGraef 0:f9b6112278fe 62 // Have more than 1 byte left to align? If not skip ahead to take care of
DieterGraef 0:f9b6112278fe 63 // trailing byte.
DieterGraef 0:f9b6112278fe 64 " cmp r1, #2\n"
DieterGraef 0:f9b6112278fe 65 " blt 7$\n"
DieterGraef 0:f9b6112278fe 66
DieterGraef 0:f9b6112278fe 67 // 4-byte align.
DieterGraef 0:f9b6112278fe 68 " ldrh r4, [r0], #2\n"
DieterGraef 0:f9b6112278fe 69 " adds r2, r2, r4\n"
DieterGraef 0:f9b6112278fe 70 " subs r1, r1, #2\n"
DieterGraef 0:f9b6112278fe 71
DieterGraef 0:f9b6112278fe 72 // Main summing loop which sums up data 2 words at a time.
DieterGraef 0:f9b6112278fe 73 // Make sure that we have more than 7 bytes left to sum.
DieterGraef 0:f9b6112278fe 74 "2$:\n"
DieterGraef 0:f9b6112278fe 75 " cmp r1, #8\n"
DieterGraef 0:f9b6112278fe 76 " blt 3$\n"
DieterGraef 0:f9b6112278fe 77 // Sum next two words. Applying previous upper 16-bit carry to
DieterGraef 0:f9b6112278fe 78 // lower 16-bits.
DieterGraef 0:f9b6112278fe 79 " ldr r4, [r0], #4\n"
DieterGraef 0:f9b6112278fe 80 " adds r2, r4\n"
DieterGraef 0:f9b6112278fe 81 " adc r2, r2, #0\n"
DieterGraef 0:f9b6112278fe 82 " ldr r4, [r0], #4\n"
DieterGraef 0:f9b6112278fe 83 " adds r2, r4\n"
DieterGraef 0:f9b6112278fe 84 " adc r2, r2, #0\n"
DieterGraef 0:f9b6112278fe 85 " subs r1, r1, #8\n"
DieterGraef 0:f9b6112278fe 86 " b 2$\n"
DieterGraef 0:f9b6112278fe 87
DieterGraef 0:f9b6112278fe 88 // Sum up any remaining half-words.
DieterGraef 0:f9b6112278fe 89 "3$:\n"
DieterGraef 0:f9b6112278fe 90 // Make sure that we have more than 1 byte left to sum.
DieterGraef 0:f9b6112278fe 91 " cmp r1, #2\n"
DieterGraef 0:f9b6112278fe 92 " blt 7$\n"
DieterGraef 0:f9b6112278fe 93 // Sum up next half word, continue to apply carry.
DieterGraef 0:f9b6112278fe 94 " ldrh r4, [r0], #2\n"
DieterGraef 0:f9b6112278fe 95 " adds r2, r4\n"
DieterGraef 0:f9b6112278fe 96 " adc r2, r2, #0\n"
DieterGraef 0:f9b6112278fe 97 " subs r1, r1, #2\n"
DieterGraef 0:f9b6112278fe 98 " b 3$\n"
DieterGraef 0:f9b6112278fe 99
DieterGraef 0:f9b6112278fe 100 // Handle trailing byte, if it exists
DieterGraef 0:f9b6112278fe 101 "7$:\n"
DieterGraef 0:f9b6112278fe 102 " cbz r1, 8$\n"
DieterGraef 0:f9b6112278fe 103 " ldrb r4, [r0]\n"
DieterGraef 0:f9b6112278fe 104 " adds r2, r4\n"
DieterGraef 0:f9b6112278fe 105 " adc r2, r2, #0\n"
DieterGraef 0:f9b6112278fe 106
DieterGraef 0:f9b6112278fe 107 // Fold 32-bit checksum into 16-bit checksum.
DieterGraef 0:f9b6112278fe 108 "8$:\n"
DieterGraef 0:f9b6112278fe 109 " ubfx r4, r2, #16, #16\n"
DieterGraef 0:f9b6112278fe 110 " ubfx r2, r2, #0, #16\n"
DieterGraef 0:f9b6112278fe 111 " adds r2, r4\n"
DieterGraef 0:f9b6112278fe 112 " ubfx r4, r2, #16, #16\n"
DieterGraef 0:f9b6112278fe 113 " ubfx r2, r2, #0, #16\n"
DieterGraef 0:f9b6112278fe 114 " adds r2, r4\n"
DieterGraef 0:f9b6112278fe 115
DieterGraef 0:f9b6112278fe 116 // Swap bytes if started at odd address
DieterGraef 0:f9b6112278fe 117 " cbz r3, 9$\n"
DieterGraef 0:f9b6112278fe 118 " rev16 r2, r2\n"
DieterGraef 0:f9b6112278fe 119
DieterGraef 0:f9b6112278fe 120 // Return final sum.
DieterGraef 0:f9b6112278fe 121 "9$: mov r0, r2\n"
DieterGraef 0:f9b6112278fe 122 " pop {r4, pc}\n"
DieterGraef 0:f9b6112278fe 123 );
DieterGraef 0:f9b6112278fe 124 }
DieterGraef 0:f9b6112278fe 125
DieterGraef 0:f9b6112278fe 126 #endif