//通过文件-传递代码进行块匹配/* * Block matching used by the file-transfer code. * * Copyright (C) 1996 Andrew Tridgell * Copyright (C) 1996 Paul Mackerras * Copyright (C) 2003-2009 Wayne Davison * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 3 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License along * with this program; if not, visit the http://fsf.org website. */#include "rsync.h"extern int verbose;extern int do_progress;extern int checksum_seed;extern int append_mode;int updating_basis_file;static int false_alarms;static int hash_hits;static int matches;static int64 data_transfer;static int total_false_alarms;static int total_hash_hits;static int total_matches;extern struct stats stats;#define TRADITIONAL_TABLESIZE (1<<16)static uint32 tablesize;static int32 *hash_table;//哈希函数#define SUM2HASH2(s1,s2) (((s1) + (s2)) & 0xFFFF)#define SUM2HASH(sum) SUM2HASH2((sum)&0xFFFF,(sum)>>16)#define BIG_SUM2HASH(sum) ((sum)%tablesize)//建立哈希表static void build_hash_table(struct sum_struct *s){static uint32 alloc_size;int32 i;//动态计算哈希表的大小，使哈希表能够容纳80%的大文件，一个比传统大小大的数必须是技术，否则s2将不能跨越整个集合/* Dynamically calculate the hash table size so that the hash load * for big files is about 80%. A number greater than the traditional * size must be odd or s2 will not be able to span the entire set. */tablesize = (uint32)(s->count/8) * 10 + 11;if (tablesize < TRADITIONAL_TABLESIZE)tablesize = TRADITIONAL_TABLESIZE;if (tablesize > alloc_size || tablesize < alloc_size - 16*1024) {if (hash_table)free(hash_table);hash_table = new_array(int32, tablesize);if (!hash_table)out_of_memory("build_hash_table");alloc_size = tablesize;}memset(hash_table, 0xFF, tablesize * sizeof hash_table[0]);if (tablesize == TRADITIONAL_TABLESIZE) {for (i = 0; i < s->count; i++) {uint32 t = SUM2HASH(s->sums[i].sum1);s->sums[i].chain = hash_table[t];hash_table[t] = i;}} else {for (i = 0; i < s->count; i++) {uint32 t = BIG_SUM2HASH(s->sums[i].sum1);s->sums[i].chain = hash_table[t];hash_table[t] = i;}}}static OFF_T last_match;//传输数据或者匹配标记//i>0表示匹配的数量，i<0表示只有数据，-1表示还会送一个0int型标记，//-2表示只送数据/* Transmit a literal and/or match token. * * This delightfully-named function is called either when we find a * match and need to transmit all the unmatched data leading up to it, * or when we get bored of accumulating literal data and just need to * transmit it. As a result of this second case, it is called even if * we have not matched at all! * * If i >= 0, the number of a matched token. If < 0, indicates we have * only literal data. A -1 will send a 0-token-int too, and a -2 sends * only literal data, w/o any token-int. */static void matched(int f, struct sum_struct *s, struct map_struct *buf, OFF_T offset, int32 i){int32 n = (int32)(offset - last_match); /* max value: block_size (int32) */int32 j;if (verbose > 2 && i >= 0) {rprintf(FINFO,"match at %.0f last_match=%.0f j=%d len=%ld n=%ld\n",(double)offset, (double)last_match, i,(long)s->sums[i].len, (long)n);}send_token(f, i, buf, last_match, n, i < 0 ? 0 : s->sums[i].len);data_transfer += n;if (i >= 0) {stats.matched_data += s->sums[i].len;n += s->sums[i].len;}for (j = 0; j < n; j += CHUNK_SIZE) {int32 n1 = MIN(CHUNK_SIZE, n - j);sum_update(map_ptr(buf, last_match + j, n1), n1);}if (i >= 0)last_match = offset + s->sums[i].len;elselast_match = offset;if (buf && do_progress)show_progress(last_match, buf->file_size);}//查找哈希表static void hash_search(int f,struct sum_struct *s,struct map_struct *buf, OFF_T len){OFF_T offset, aligned_offset, end;int32 k, want_i, aligned_i, backup;char sum2[SUM_LENGTH];uint32 s1, s2, sum;int more;schar *map;//want_i变量用来支持邻近匹配，允许RLL输出代码使运行更有效率/* want_i is used to encourage adjacent matches, allowing the RLL * coding of the output to work more efficiently. */want_i = 0;if (verbose > 2) {rprintf(FINFO, "hash search b=%ld len=%.0f\n",(long)s->blength, (double)len);}k = (int32)MIN(len, (OFF_T)s->blength);map = (schar *)map_ptr(buf, 0, k);sum = get_checksum1((char *)map, k);s1 = sum & 0xFFFF;s2 = sum >> 16;if (verbose > 3)rprintf(FINFO, "sum=%.8x k=%ld\n", sum, (long)k);offset = aligned_offset = aligned_i = 0;end = len + 1 - s->sums[s->count-1].len;if (verbose > 3) {rprintf(FINFO, "hash search s->blength=%ld len=%.0f count=%.0f\n",(long)s->blength, (double)len, (double)s->count);}do {int done_csum2 = 0;int32 i;if (verbose > 4) {rprintf(FINFO, "offset=%.0f sum=%04x%04x\n",(double)offset, s2 & 0xFFFF, s1 & 0xFFFF);}if (tablesize == TRADITIONAL_TABLESIZE) {if ((i = hash_table[SUM2HASH2(s1,s2)]) < 0)goto null_hash;sum = (s1 & 0xffff) | (s2 << 16);} else {sum = (s1 & 0xffff) | (s2 << 16);if ((i = hash_table[BIG_SUM2HASH(sum)]) < 0)goto null_hash;}hash_hits++;do {int32 l;if (sum != s->sums[i].sum1)continue;//同时确保两个块有相同长度/* also make sure the two blocks are the same length */l = (int32)MIN((OFF_T)s->blength, len-offset);if (l != s->sums[i].len)continue;//保证块偏移要么>=我们的偏移量，要么不移动/* in-place: ensure chunk's offset is either >= our * offset or that the data didn't move. */if (updating_basis_file && s->sums[i].offset < offset && !(s->sums[i].flags & SUMFLG_SAME_OFFSET))continue;if (verbose > 3) {rprintf(FINFO,"potential match at %.0f i=%ld sum=%08x\n",(double)offset, (long)i, sum);}if (!done_csum2) {map = (schar *)map_ptr(buf,offset,l);get_checksum2((char *)map,l,sum2);done_csum2 = 1;}if (memcmp(sum2,s->sums[i].sum2,s->s2length) != 0) {false_alarms++;continue;}//当更新原位时，最可能的匹配是用一个完全相同的偏移量，所以我们//希望在邻近的want_i最佳化/* When updating in-place, the best possible match is * one with an identical offset, so we prefer that over * the adjacent want_i optimization. */if (updating_basis_file) {/* All the generator's chunks start at blength boundaries. */while (aligned_offset < offset) {aligned_offset += s->blength;aligned_i++;}if (offset == aligned_offset && aligned_i < s->count) {if (i != aligned_i) {if (sum != s->sums[aligned_i].sum1 || l != s->sums[aligned_i].len || memcmp(sum2, s->sums[aligned_i].sum2, s->s2length) != 0)goto check_want_i;i = aligned_i;}//这个块在老的和新的文件的同一地点/* This identical chunk is in the same spot in the old and new file. */s->sums[i].flags |= SUMFLG_SAME_OFFSET;want_i = i;}}check_want_i://我们已经找到了一个匹配，但现在检验want_i是否能够示意一个更好的匹配/* we've found a match, but now check to see * if want_i can hint at a better match. */if (i != want_i && want_i < s->count && (!updating_basis_file || s->sums[want_i].offset >= offset || s->sums[want_i].flags & SUMFLG_SAME_OFFSET) && sum == s->sums[want_i].sum1 && memcmp(sum2, s->sums[want_i].sum2, s->s2length) == 0) {//我们已经找到了一个邻近匹配——RLL编码员很开心/* we've found an adjacent match - the RLL coder * will be happy */i = want_i;}want_i = i + 1;matched(f,s,buf,offset,i);offset += s->sums[i].len - 1;k = (int32)MIN((OFF_T)s->blength, len-offset);map = (schar *)map_ptr(buf, offset, k);sum = get_checksum1((char *)map, k);s1 = sum & 0xFFFF;s2 = sum >> 16;matches++;break;} while ((i = s->sums[i].chain) >= 0); null_hash:backup = (int32)(offset - last_match);//我们有时先读取一个字节到最后匹配/* We sometimes read 1 byte prior to last_match... */if (backup < 0)backup = 0;//修剪校验和的第一个字节/* Trim off the first byte from the checksum */more = offset + k < len;map = (schar *)map_ptr(buf, offset - backup, k + more + backup) + backup;s1 -= map[0] + CHAR_OFFSET;s2 -= k * (map[0]+CHAR_OFFSET);//增加下一个字节（如果有的话）到校验和/* Add on the next byte (if there is one) to the checksum */if (more) {s1 += map[k] + CHAR_OFFSET;s2 += s1;} else--k;//通过早早匹配，我们避免重复读取数据三次当一个标记//自从上次匹配后走了很长一段路过来//这3次读取由运行时的匹配，校验和更新和数据发送引起/* By matching early we avoid re-reading the data 3 times in the case where a token match comes a long way after last match. The 3 reads are caused by the running match, the checksum update and the literal send. */if (backup >= s->blength+CHUNK_SIZE && end-offset > CHUNK_SIZE)matched(f, s, buf, offset - s->blength, -2);} while (++offset < end);matched(f, s, buf, len, -1);map_ptr(buf, len-1, 1);}//浏览一个原文件，从生成器中寻找匹配校验和的块，然后传输数据或标记//同时也用md计算器计算整个文件的md4校验和，这和文件一起传输，为了避免线路的故障//参数：s，是来自生成器的校验和，如果<tt>s->count ==0</tt>，那么这个文件没有//校验和//参数：len，是将要传输文件的长度/** * Scan through a origin file, looking for sections that match * checksums from the generator, and transmit either literal or token * data. * * Also calculates the MD4 checksum of the whole file, using the md * accumulator. This is transmitted with the file as protection * against corruption on the wire. * * @param s Checksums received from the generator. If <tt>s->count == * 0</tt>, then there are actually no checksums for this file. * * @param len Length of the file to send. **/void match_sums(int f, struct sum_struct *s, struct map_struct *buf, OFF_T len){char file_sum[MAX_DIGEST_LEN];int sum_len;last_match = 0;false_alarms = 0;hash_hits = 0;matches = 0;data_transfer = 0;sum_init(checksum_seed);if (append_mode > 0) {if (append_mode == 2) {OFF_T j = 0;for (j = CHUNK_SIZE; j < s->flength; j += CHUNK_SIZE) {if (buf && do_progress)show_progress(last_match, buf->file_size);sum_update(map_ptr(buf, last_match, CHUNK_SIZE), CHUNK_SIZE);last_match = j;}if (last_match < s->flength) {int32 n = (int32)(s->flength - last_match);if (buf && do_progress)show_progress(last_match, buf->file_size);sum_update(map_ptr(buf, last_match, n), n);}}last_match = s->flength;s->count = 0;}if (len > 0 && s->count > 0) {build_hash_table(s);if (verbose > 2)rprintf(FINFO,"built hash table\n");hash_search(f, s, buf, len);if (verbose > 2)rprintf(FINFO,"done hash search\n");} else {OFF_T j;//通过这个，我们避免了很多查找/* by doing this in pieces we avoid too many seeks */for (j = last_match + CHUNK_SIZE; j < len; j += CHUNK_SIZE)matched(f, s, buf, j, -2);matched(f, s, buf, len, -1);}sum_len = sum_end(file_sum);//如果读取错误，传输坏校验码/* If we had a read error, send a bad checksum. */if (buf && buf->status != 0)file_sum[0]++;if (verbose > 2)rprintf(FINFO,"sending file_sum\n");write_buf(f, file_sum, sum_len);if (verbose > 2)rprintf(FINFO, "false_alarms=%d hash_hits=%d matches=%d\n",false_alarms, hash_hits, matches);total_hash_hits += hash_hits;total_false_alarms += false_alarms;total_matches += matches;stats.literal_data += data_transfer;}//匹配报告void match_report(void){if (verbose <= 1)return;rprintf(FINFO,"total: matches=%d hash_hits=%d false_alarms=%d data=%.0f\n",total_matches, total_hash_hits, total_false_alarms,(double)stats.literal_data);}
