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From: | Shannon Zhao |
Subject: | Re: [Qemu-devel] [PATCH v5 13/20] hw/acpi/aml-build: Add ToUUID macro |
Date: | Wed, 29 Apr 2015 21:41:39 +0800 |
User-agent: | Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 |
On 2015/4/28 17:48, Shannon Zhao wrote:
On 2015/4/28 17:35, Igor Mammedov wrote:On Tue, 28 Apr 2015 16:52:19 +0800 Shannon Zhao <address@hidden> wrote:On 2015/4/28 16:15, Igor Mammedov wrote:btw:whole thing might be simpler if an intermediate conversion is avoided, just pack buffer as in spec byte by byte: /* format: aabbccdd-eeff-gghh-iijj-kkllmmnnoopp */ assert(strlen(uuid) == ...); build_append_byte(var->buf, HEX2BYTE(uuid[3]); /* dd */use build_append_byte(var->buf, HEX2BYTE(uuid + 7); ?build_append_byte(var->buf, HEX2BYTE(uuid[2]); /* cc */use build_append_byte(var->buf, HEX2BYTE(uuid + 5); ?if you mean hyphens /-/ then they are not encoded, but you surely can add checks for them to make sure that UUID format is as expected.I mean uuid[3] points to b not dd. Maybe use following way: static uint8_t Hex2Byte(char *src)or even better: Hex2Byte(char *src, byte_idx) and do pointer arithmetic inside [...]build_append_byte(var->buf, Hex2Byte(uuid + (3 * 2))); /* dd */build_append_byte(var->buf, Hex2Byte(uuid, 3)); /* dd - at offset 00 */ build_append_byte(var->buf, Hex2Byte(uuid, 2)); /* cc - at offset 01 */ ...Yes, it's better to first four bytes. But there are hyphens /-/, for offset 04, 05 and etc it doesn't work. We can't use following expression: build_append_byte(var->buf, Hex2Byte(uuid, 5)); /* ff - at offset 04 */ build_append_byte(var->buf, Hex2Byte(uuid, 4)); /* ee - at offset 05 */ ...
So about the implementation of this macro, I think I'd like to use following approach. This lets Hex2Byte do what it should only do and still has a clear look of UUID. What do you think about?
static uint8_t Hex2Byte(char *src) { int hi = Hex2Digit(*src++); int lo = Hex2Digit(*src); if ((hi < 0) || (lo < 0)) return -1; return (hi << 4) | lo; } g_assert((strlen(uuid) == 36) && (uuid[8] == '-') && (uuid[13] == '-') && (uuid[18] == '-') && (uuid[23] == '-')); build_append_byte(var->buf, Hex2Byte(uuid + (3 * 2))); /* dd */ build_append_byte(var->buf, Hex2Byte(uuid + (2 * 2))); /* cc */ build_append_byte(var->buf, Hex2Byte(uuid + (1 * 2))); /* bb */ build_append_byte(var->buf, Hex2Byte(uuid + (0 * 2))); /* aa */ build_append_byte(var->buf, Hex2Byte(uuid + (5 * 2 + 1))); /* ff */ build_append_byte(var->buf, Hex2Byte(uuid + (4 * 2 + 1))); /* ee */ build_append_byte(var->buf, Hex2Byte(uuid + (7 * 2 + 2))); /* hh */ build_append_byte(var->buf, Hex2Byte(uuid + (6 * 2 + 2))); /* gg */ build_append_byte(var->buf, Hex2Byte(uuid + (8 * 2 + 3))); /* ii */ build_append_byte(var->buf, Hex2Byte(uuid + (9 * 2 + 3))); /* jj */ build_append_byte(var->buf, Hex2Byte(uuid + (10 * 2 + 4))); /* kk */ build_append_byte(var->buf, Hex2Byte(uuid + (11 * 2 + 4))); /* ll */ build_append_byte(var->buf, Hex2Byte(uuid + (12 * 2 + 4))); /* mm */ build_append_byte(var->buf, Hex2Byte(uuid + (13 * 2 + 4))); /* nn */ build_append_byte(var->buf, Hex2Byte(uuid + (14 * 2 + 4))); /* oo */ build_append_byte(var->buf, Hex2Byte(uuid + (15 * 2 + 4))); /* pp */
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