IBM Watson IoT / Mbed OS IBMIoTClientEthernetExample

Contains example code to connect the mbed LPC1768 or FRDM-K64F devices to the IBM Internet of Things Cloud service via ethernet.

Dependencies:   C12832 MQTT LM75B MMA7660

Dependents:   MFT_IoT_demo_USB400 IBM_RFID

EthernetInterface/lwip-sys/arch/checksum.c@6:37b6d0d56190, 2014-08-20 (annotated)

Committer:
samdanbury
Date:
Wed Aug 20 12:45:14 2014 +0000
Revision:
6:37b6d0d56190
Code completely changed to improve the structure, flow and memory usage of the application

Who changed what in which revision?

UserRevisionLine numberNew contents of line
samdanbury 6:37b6d0d56190 1 /* Copyright (C) 2013 - Adam Green (https://github.com/adamgreen)
samdanbury 6:37b6d0d56190 2
samdanbury 6:37b6d0d56190 3 Licensed under the Apache License, Version 2.0 (the "License");
samdanbury 6:37b6d0d56190 4 you may not use this file except in compliance with the License.
samdanbury 6:37b6d0d56190 5 You may obtain a copy of the License at
samdanbury 6:37b6d0d56190 6
samdanbury 6:37b6d0d56190 7 http://www.apache.org/licenses/LICENSE-2.0
samdanbury 6:37b6d0d56190 8
samdanbury 6:37b6d0d56190 9 Unless required by applicable law or agreed to in writing, software
samdanbury 6:37b6d0d56190 10 distributed under the License is distributed on an "AS IS" BASIS,
samdanbury 6:37b6d0d56190 11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
samdanbury 6:37b6d0d56190 12 See the License for the specific language governing permissions and
samdanbury 6:37b6d0d56190 13 limitations under the License.
samdanbury 6:37b6d0d56190 14 */
samdanbury 6:37b6d0d56190 15 #if defined(TOOLCHAIN_GCC) && defined(__thumb2__)
samdanbury 6:37b6d0d56190 16
samdanbury 6:37b6d0d56190 17
samdanbury 6:37b6d0d56190 18 /* This is a hand written Thumb-2 assembly language version of the
samdanbury 6:37b6d0d56190 19 algorithm 3 version of lwip_standard_chksum in lwIP's inet_chksum.c. It
samdanbury 6:37b6d0d56190 20 performs the checksumming 32-bits at a time and even unrolls the loop to
samdanbury 6:37b6d0d56190 21 perform two of these 32-bit adds per loop iteration.
samdanbury 6:37b6d0d56190 22
samdanbury 6:37b6d0d56190 23 Returns:
samdanbury 6:37b6d0d56190 24 16-bit 1's complement summation (not inversed).
samdanbury 6:37b6d0d56190 25
samdanbury 6:37b6d0d56190 26 NOTE: This function does return a uint16_t from the assembly language code
samdanbury 6:37b6d0d56190 27 but is marked as void so that GCC doesn't issue warning because it
samdanbury 6:37b6d0d56190 28 doesn't know about this low level return.
samdanbury 6:37b6d0d56190 29 */
samdanbury 6:37b6d0d56190 30 __attribute__((naked)) void /*uint16_t*/ thumb2_checksum(const void* pData, int length)
samdanbury 6:37b6d0d56190 31 {
samdanbury 6:37b6d0d56190 32 __asm (
samdanbury 6:37b6d0d56190 33 ".syntax unified\n"
samdanbury 6:37b6d0d56190 34 ".thumb\n"
samdanbury 6:37b6d0d56190 35
samdanbury 6:37b6d0d56190 36 // Push non-volatile registers we use on stack. Push link register too to
samdanbury 6:37b6d0d56190 37 // keep stack 8-byte aligned and allow single pop to restore and return.
samdanbury 6:37b6d0d56190 38 " push {r4, lr}\n"
samdanbury 6:37b6d0d56190 39 // Initialize sum, r2, to 0.
samdanbury 6:37b6d0d56190 40 " movs r2, #0\n"
samdanbury 6:37b6d0d56190 41 // Remember whether pData was at odd address in r3. This is used later to
samdanbury 6:37b6d0d56190 42 // know if it needs to swap the result since the summation will be done at
samdanbury 6:37b6d0d56190 43 // an offset of 1, rather than 0.
samdanbury 6:37b6d0d56190 44 " ands r3, r0, #1\n"
samdanbury 6:37b6d0d56190 45 // Need to 2-byte align? If not skip ahead.
samdanbury 6:37b6d0d56190 46 " beq 1$\n"
samdanbury 6:37b6d0d56190 47 // We can return if there are no bytes to sum.
samdanbury 6:37b6d0d56190 48 " cbz r1, 9$\n"
samdanbury 6:37b6d0d56190 49
samdanbury 6:37b6d0d56190 50 // 2-byte align.
samdanbury 6:37b6d0d56190 51 // Place the first data byte in odd summation location since it needs to be
samdanbury 6:37b6d0d56190 52 // swapped later. It's ok to overwrite r2 here as it only had a value of 0
samdanbury 6:37b6d0d56190 53 // up until now. Advance r0 pointer and decrement r1 length as we go.
samdanbury 6:37b6d0d56190 54 " ldrb r2, [r0], #1\n"
samdanbury 6:37b6d0d56190 55 " lsls r2, r2, #8\n"
samdanbury 6:37b6d0d56190 56 " subs r1, r1, #1\n"
samdanbury 6:37b6d0d56190 57
samdanbury 6:37b6d0d56190 58 // Need to 4-byte align? If not skip ahead.
samdanbury 6:37b6d0d56190 59 "1$:\n"
samdanbury 6:37b6d0d56190 60 " ands r4, r0, #3\n"
samdanbury 6:37b6d0d56190 61 " beq 2$\n"
samdanbury 6:37b6d0d56190 62 // Have more than 1 byte left to align? If not skip ahead to take care of
samdanbury 6:37b6d0d56190 63 // trailing byte.
samdanbury 6:37b6d0d56190 64 " cmp r1, #2\n"
samdanbury 6:37b6d0d56190 65 " blt 7$\n"
samdanbury 6:37b6d0d56190 66
samdanbury 6:37b6d0d56190 67 // 4-byte align.
samdanbury 6:37b6d0d56190 68 " ldrh r4, [r0], #2\n"
samdanbury 6:37b6d0d56190 69 " adds r2, r2, r4\n"
samdanbury 6:37b6d0d56190 70 " subs r1, r1, #2\n"
samdanbury 6:37b6d0d56190 71
samdanbury 6:37b6d0d56190 72 // Main summing loop which sums up data 2 words at a time.
samdanbury 6:37b6d0d56190 73 // Make sure that we have more than 7 bytes left to sum.
samdanbury 6:37b6d0d56190 74 "2$:\n"
samdanbury 6:37b6d0d56190 75 " cmp r1, #8\n"
samdanbury 6:37b6d0d56190 76 " blt 3$\n"
samdanbury 6:37b6d0d56190 77 // Sum next two words. Applying previous upper 16-bit carry to
samdanbury 6:37b6d0d56190 78 // lower 16-bits.
samdanbury 6:37b6d0d56190 79 " ldr r4, [r0], #4\n"
samdanbury 6:37b6d0d56190 80 " adds r2, r4\n"
samdanbury 6:37b6d0d56190 81 " adc r2, r2, #0\n"
samdanbury 6:37b6d0d56190 82 " ldr r4, [r0], #4\n"
samdanbury 6:37b6d0d56190 83 " adds r2, r4\n"
samdanbury 6:37b6d0d56190 84 " adc r2, r2, #0\n"
samdanbury 6:37b6d0d56190 85 " subs r1, r1, #8\n"
samdanbury 6:37b6d0d56190 86 " b 2$\n"
samdanbury 6:37b6d0d56190 87
samdanbury 6:37b6d0d56190 88 // Sum up any remaining half-words.
samdanbury 6:37b6d0d56190 89 "3$:\n"
samdanbury 6:37b6d0d56190 90 // Make sure that we have more than 1 byte left to sum.
samdanbury 6:37b6d0d56190 91 " cmp r1, #2\n"
samdanbury 6:37b6d0d56190 92 " blt 7$\n"
samdanbury 6:37b6d0d56190 93 // Sum up next half word, continue to apply carry.
samdanbury 6:37b6d0d56190 94 " ldrh r4, [r0], #2\n"
samdanbury 6:37b6d0d56190 95 " adds r2, r4\n"
samdanbury 6:37b6d0d56190 96 " adc r2, r2, #0\n"
samdanbury 6:37b6d0d56190 97 " subs r1, r1, #2\n"
samdanbury 6:37b6d0d56190 98 " b 3$\n"
samdanbury 6:37b6d0d56190 99
samdanbury 6:37b6d0d56190 100 // Handle trailing byte, if it exists
samdanbury 6:37b6d0d56190 101 "7$:\n"
samdanbury 6:37b6d0d56190 102 " cbz r1, 8$\n"
samdanbury 6:37b6d0d56190 103 " ldrb r4, [r0]\n"
samdanbury 6:37b6d0d56190 104 " adds r2, r4\n"
samdanbury 6:37b6d0d56190 105 " adc r2, r2, #0\n"
samdanbury 6:37b6d0d56190 106
samdanbury 6:37b6d0d56190 107 // Fold 32-bit checksum into 16-bit checksum.
samdanbury 6:37b6d0d56190 108 "8$:\n"
samdanbury 6:37b6d0d56190 109 " ubfx r4, r2, #16, #16\n"
samdanbury 6:37b6d0d56190 110 " ubfx r2, r2, #0, #16\n"
samdanbury 6:37b6d0d56190 111 " adds r2, r4\n"
samdanbury 6:37b6d0d56190 112 " ubfx r4, r2, #16, #16\n"
samdanbury 6:37b6d0d56190 113 " ubfx r2, r2, #0, #16\n"
samdanbury 6:37b6d0d56190 114 " adds r2, r4\n"
samdanbury 6:37b6d0d56190 115
samdanbury 6:37b6d0d56190 116 // Swap bytes if started at odd address
samdanbury 6:37b6d0d56190 117 " cbz r3, 9$\n"
samdanbury 6:37b6d0d56190 118 " rev16 r2, r2\n"
samdanbury 6:37b6d0d56190 119
samdanbury 6:37b6d0d56190 120 // Return final sum.
samdanbury 6:37b6d0d56190 121 "9$: mov r0, r2\n"
samdanbury 6:37b6d0d56190 122 " pop {r4, pc}\n"
samdanbury 6:37b6d0d56190 123 );
samdanbury 6:37b6d0d56190 124 }
samdanbury 6:37b6d0d56190 125
samdanbury 6:37b6d0d56190 126 #endif