{"id":120,"date":"2020-07-23T23:39:24","date_gmt":"2020-07-23T15:39:24","guid":{"rendered":"http:\/\/www.peijy.top\/?p=120"},"modified":"2022-05-16T11:41:12","modified_gmt":"2022-05-16T03:41:12","slug":"csapp-%e4%b9%a0%e9%a2%983-4","status":"publish","type":"post","link":"https:\/\/www.eutaboo.com\/index.php\/2020\/07\/23\/csapp-%e4%b9%a0%e9%a2%983-4\/","title":{"rendered":"CSAPP \u4e60\u98983.4"},"content":{"rendered":"

\u9898\u76ee<\/h2>\r\n\r\n\r\n\r\n

\u5047\u8bbe\u53d8\u91cfsp\u548cdp\u88ab\u58f0\u660e\u4e3a\u7c7b\u578b<\/p>\r\n\r\n\r\n\r\n

src_t *sp;
dest_t *dp;
\u8fd9\u91ccsrc_t\u548cdest_t\u662f\u7528typedef\u58f0\u660e\u7684\u6570\u636e\u7c7b\u578b\u3002\u6211\u4eec\u60f3\u4f7f\u7528\u9002\u5f53\u7684\u6570\u636e\u4f20\u9001\u6307\u4ee4\u6765\u5b9e\u73b0\u4e0b\u9762\u7684\u64cd\u4f5c
*dp = (dest_t) *sp;<\/p>\r\n\r\n\r\n\r\n

\u5047\u8bbesp\u548cdp\u7684\u503c\u5206\u522b\u5b58\u50a8\u5728\u5bc4\u5b58\u5668%rdi\u548c%rsi\u4e2d\u3002\u5bf9\u4e8e\u8868\u4e2d\u7684\u6bcf\u4e2a\u8868\u9879\uff0c\u7ed9\u51fa\u5b9e\u73b0\u6307\u4ee4\u6570\u636e\u4f20\u9001\u7684\u4e24\u6761\u6307\u4ee4\u3002\u5176\u4e2d\u7b2c\u4e00\u6761\u6307\u4ee4\u5e94\u8be5\u4ece\u5185\u5b58\u4e2d\u8bfb\u6570\uff0c\u505a\u9002\u5f53\u7684\u8f6c\u6362\uff0c\u5e76\u8bbe\u7f6e\u5bc4\u5b58\u5668%rax\u7684\u9002\u5f53\u90e8\u5206\u3002\u7136\u540e\uff0c\u7b2c\u4e8c\u6761\u6307\u4ee4\u8981\u628a%rax\u7684\u9002\u5f53\u90e8\u5206\u5199\u5230\u5185\u5b58\u3002\u5728\u8fd9\u4e24\u79cd\u60c5\u51b5\u4e2d\uff0c\u5bc4\u5b58\u5668\u7684\u90e8\u5206\u53ef\u4ee5\u4f7f%rax\u3001%eax\u3001%ax\u6216%al\uff0c\u4e24\u8005\u53ef\u4ee5\u4e92\u4e0d\u76f8\u540c\u3002
\u8bb0\u4f4f\uff0c\u5f53\u6267\u884c\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\u65e2\u6d89\u53ca\u5927\u5c0f\u53d8\u5316\u53c8\u6d89\u53caC\u8bed\u8a00\u4e2d\u7b26\u53f7\u53d8\u5316\u65f6\uff0c\u64cd\u4f5c\u5e94\u5148\u6539\u53d8\u5927\u5c0f\u3002<\/p>\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n
src_t<\/th>\r\ndest_t<\/th>\r\n\u6307\u4ee4<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
long<\/td>\r\nlong<\/td>\r\nmovq (%rdi),%rax
movq %rax,(%rsi)<\/td>\r\n<\/tr>\r\n
char<\/td>\r\nint<\/td>\r\n\u00a0<\/td>\r\n<\/tr>\r\n
char<\/td>\r\nunsigned<\/td>\r\n\u00a0<\/td>\r\n<\/tr>\r\n
unsigned char<\/td>\r\nlong<\/td>\r\n\u00a0<\/td>\r\n<\/tr>\r\n
int<\/td>\r\nchar<\/td>\r\n\u00a0<\/td>\r\n<\/tr>\r\n
unsigned<\/td>\r\nunsigned char<\/td>\r\n\u00a0<\/td>\r\n<\/tr>\r\n
char<\/td>\r\nshort<\/td>\r\n\u00a0<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n\r\n\r\n\r\n

\u89e3\u7b54<\/h2>\r\n\r\n\r\n\r\n

\u8fd9\u4e2a\u9898\u76ee\u672c\u8eab\u4e0d\u96be\uff0c\u4f46\u662f\u6709\u4e00\u70b9\u5f88\u7ed5\uff0c\u4ec0\u4e48\u65f6\u5019\u7528\u7b26\u53f7\u6269\u5c55\u4f20\u9001\u6307\u4ee4\uff0c\u4ec0\u4e48\u65f6\u5019\u7528\u96f6\u6269\u5c55\u4f20\u9001\u6307\u4ee4<\/p>\r\n\r\n\r\n\r\n

\u9996\u5148\uff0c\u6839\u636e\u5de6\u53f3\u4e24\u4e2a\u7684\u6700\u5927\u957f\u5ea6\u6765\u5224\u65ad\u662f%rax\u3001%eax\u3001%ax\u8fd8\u662f%al\u3002\u5982\uff1achar\u662f\u4e00\u5b57\u8282\uff0cint\u662f\u53cc\u5b57\uff0c\u6240\u4ee5\u7528%eax\uff1bchar\u662f\u4e00\u5b57\u8282\uff0cshort\u662f\u4e00\u5b57\uff0c\u6240\u4ee5\u7528%ax\u3002<\/p>\r\n\r\n\r\n\r\n

\u6211\u4eec\u4e00\u884c\u4e00\u884c\u89e3\u7b54<\/p>\r\n\r\n\r\n\r\n

1. char -> int<\/p>\r\n\r\n\r\n\r\n

\u9996\u5148char\u662f\u6709\u7b26\u53f7\u7c7b\u578b\uff0cint\u4e5f\u662f\u6709\u7b26\u53f7\u7c7b\u578b\uff0c\u6240\u4ee5\u53ef\u4ee5\u80af\u5b9a\u9700\u8981\u7b26\u53f7\u6269\u5c55\u4f20\u9001\u6307\u4ee4\uff0c\u7531\u4e8echar\u662f1\u5b57\u8282\uff0c\u800cint\u662f\u662f\u53cc\u5b57\uff0c\u6240\u4ee5\u7ed3\u679c\u5e94\u8be5\u4e3a
movsbl (%rdi),%eax
movq %eax,(%rsi)<\/p>\r\n\r\n\r\n\r\n

2. char -> unsigned<\/p>\r\n\r\n\r\n\r\n

\u7531\u4e8echar\u662f\u6709\u7b26\u53f7\u7c7b\u578b\uff0cunsigned\u662f\u65e0\u7b26\u53f7\u7c7b\u578b\uff0c\u90a3\u4e48\u4e00\u4e2a\u6709\u7b26\u53f7\u4e00\u4e2a\u65e0\u7b26\u53f7\uff0c\u6211\u600e\u4e48\u9009\u62e9\u6269\u5c55\u6307\u4ee4\u5462\uff0c\u8fd9\u662f\u9898\u76ee\u7684\u90a3\u53e5\uff0c\u8bb0\u4f4f\uff0c\u5f53\u6267\u884c\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\u65e2\u6d89\u53ca\u5927\u5c0f\u53d8\u5316\u53c8\u6d89\u53caC\u8bed\u8a00\u4e2d\u7b26\u53f7\u53d8\u5316\u65f6\uff0c\u64cd\u4f5c\u5e94\u5148\u6539\u53d8\u5927\u5c0f\u3002\uff0c\u6240\u4ee5\u6211\u4eec\u5e94\u8be5\u5148\u6539\u53d8\u5927\u5c0f\uff0c\u6539\u53d8\u6709\u7b26\u53f7\u6570\u7684\u5927\u5c0f\u8fd8\u662f\u5e94\u8be5\u7528movqs\u6307\u4ee4\uff0c\u6240\u4ee5\u7ed3\u679c\u4e0e\u4e0a\u9762\u76f8\u540c\uff0c
movsbl (%rdi),%eax
movq %eax,(%rsi)<\/p>\r\n\r\n\r\n\r\n

3. unsigned char -> long<\/p>\r\n\r\n\r\n\r\n

\u73b0\u5728\u53c8\u6765\u4e86\uff0c\u7b2c\u4e00\u4e2a\u662f\u65e0\u7b26\u53f7\u6570\uff0c\u7b2c\u4e8c\u4e2a\u662f\u6709\u7b26\u53f7\u6570\uff0c\u7b2c\u4e00\u4e2a\u662f\u4e00\u5b57\u8282\uff0c\u7b2c\u4e8c\u4e2a\u662f4\u5b57\uff0c\u6839\u636e\u4e0a\u9762\u7684\u539f\u5219\u5e94\u8be5\u5148\u6539\u53d8\u5927\u5c0f\uff0c
movzbq (%rdi),%eax
movq %rax,(%rsi),
\u7b49\u7b49\u4e3a\u4ec0\u4e48\u7b54\u6848\u4e0d\u5bf9\uff0c\u4e3a\u4ec0\u4e48\u7b54\u6848\u662f
movzbl(%rdi),%eax
movq %rax,(%rsi)
\u8bfe\u672cP123\u9875\u7ed9\u51fa\uff0cmovl\u6307\u4ee4\u4ee5\u5bc4\u5b58\u5668\u4f5c\u4e3a\u76ee\u7684\u65f6\uff0c\u5b83\u4f1a\u628a\u8be5\u5bc4\u5b58\u5668\u7684\u9ad8\u4f4d4\u5b57\u8282\u8bbe\u7f6e\u4e3a0\u3002\u5927\u610f\u662f\u628a32\u4f4d\u6269\u5c55\u523064\u4f4d\u3002<\/p>\r\n\r\n\r\n\r\n

4. int -> char<\/p>\r\n\r\n\r\n\r\n

\u8fd9\u4e2a\u57fa\u672c\u4e0a\u5c31\u6ca1\u6709\u4ec0\u4e48\u8981\u8bb2\u7684\u4e86\uff0cint\u6709\u7b26\u53f7\uff0cchar\u6709\u7b26\u53f7\uff0c\u4e5f\u4e0d\u9700\u8981\u6269\u5c55\uff0c
movl (%rdi),%eax
movq %al,(%rsi)<\/p>\r\n\r\n\r\n\r\n

5. unsigned -> unsigned char<\/p>\r\n\r\n\r\n\r\n

\u8fd9\u4e2a\u7b54\u6848\u4e5f\u5f88\u7b80\u5355\uff0c
movl (%rdi),%eax
movq %al,(%rsi)<\/p>\r\n\r\n\r\n\r\n

6. char -> short<\/p>\r\n\r\n\r\n\r\n

\u8fd9\u4e2a\u4e5f\u4e0d\u96be\u4e86\uff0cchar\u662f\u6709\u7b26\u53f7\u4e00\u4e2a\u5b57\u8282\uff0cshort\u662f\u6709\u7b26\u53f7\u7684\u4e00\u4e2a\u5b57\uff0c\u6240\u4ee5\u7b54\u6848\u662f
movsbw (%rdi),%ax
movw %ax,(%rsi)<\/p>\r\n","protected":false},"excerpt":{"rendered":"

\u9898\u76ee \u5047\u8bbe\u53d8\u91cfsp\u548cdp\u88ab\u58f0\u660e\u4e3a\u7c7b\u578b src_t *sp;dest_t *dp;\u8fd9\u91ccsrc_t\u548cdest_t\u662f\u7528typedef\u58f0\u660e …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"emotion":"","emotion_color":"","title_style":"","license":"","footnotes":""},"categories":[9],"tags":[18,60,62],"class_list":["post-120","post","type-post","status-publish","format-standard","hentry","category-9","tag-csapp","tag-60","tag-62"],"_links":{"self":[{"href":"https:\/\/www.eutaboo.com\/index.php\/wp-json\/wp\/v2\/posts\/120","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.eutaboo.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.eutaboo.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.eutaboo.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.eutaboo.com\/index.php\/wp-json\/wp\/v2\/comments?post=120"}],"version-history":[{"count":0,"href":"https:\/\/www.eutaboo.com\/index.php\/wp-json\/wp\/v2\/posts\/120\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.eutaboo.com\/index.php\/wp-json\/wp\/v2\/media?parent=120"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.eutaboo.com\/index.php\/wp-json\/wp\/v2\/categories?post=120"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.eutaboo.com\/index.php\/wp-json\/wp\/v2\/tags?post=120"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}