add page

CMakeLists.txt

@@ -8,7 +8,8 @@ if(${isBigEndian})
     add_definitions(-DWORDS_BIGENDIAN)
 endif()
 
-option(BUILD_TEST "Whether to build tests" OFF)
+include(option.txt)
+
 if(${BUILD_TEST})
     message(STATUS "Building tests...")
     enable_testing()

README.md

@@ -13,5 +13,8 @@ Most part of this README and the docs in `api` folder is written in Chinese. If
 - [ ] 按索引[删除表项](/api/table.md#表项的删除)
 - [ ] 对非主键（无[unique约束](/api/types.md#类型修饰符)）进行[索引](/api/index.md)
 
+## 关于并发
+不支持并发，如需要并发，请自行加锁以免数据损坏。
+
 ## Thanks
 - [asciiflow](https://asciiflow.com/)

api/dbfile.md

@@ -34,7 +34,7 @@
 #### 新建
 空闲块不会被主动新建，而是源于分配时富余的部分以及删除后的剩余。
 #### 合并
-受限于记录长度的数字为uint16，一块未被使用的空闲空间大小最大为`65535`，一般则不使其超过`32768`。如果确有连续的超过`32768`字节的空闲，应当划分为多个块。特别地，如果确有连续的超过`32768`字节的空闲且其后的空间不足`4096`字节，应当适当减小前一块的大小，使后一块大小超过`4096`字节。
+受限于记录长度的数字为uint16，一块未被使用的空闲空间大小最大为`65535`，实际使用时不使其超过`4096`。如果确有连续的超过`4096`字节的空闲，应当划分为多个块。块应当是`4k`对齐的。
 #### 使用
 使用时优先从第一个块遍历，比较其大小以及页对齐是否符合要求。当使用后仍有剩余，对于小于10字节的块，直接舍弃不用；否则更新块大小与相关链表指针。
 ### 表

include/binary.h

@@ -1,3 +1,6 @@
+#ifndef _BINARY_H_
+#define _BINARY_H_
+
 #include <stdio.h>
 #include <stdint.h>
 #include <stdlib.h>
@@ -48,19 +51,53 @@
         #define putle16(buf, x) (*(uint16_t*)(buf) = _byteswap_ushort((uint16_t)(x)))
         #define putle32(buf, x) (*(uint32_t*)(buf) = _byteswap_ulong((uint32_t)(x)))
         #define putle64(buf, x) (*(uint64_t*)(buf) = _byteswap_uint64((uint64_t)(x)))
+
+        #define readle16(fd, num) ((~read((fd), &(num), 2))?((num)=_byteswap_ushort((uint16_t)(num))):EOF)
+        #define readle32(fd, num) ((~read((fd), &(num), 4))?((num)=_byteswap_ulong((uint32_t)(num))):EOF)
+        #define readle64(fd, num) ((~read((fd), &(num), 8))?((num)=_byteswap_uint64((uint64_t)(num))):EOF)
+
+        #define le16(buf) _byteswap_ushort(*(uint16_t*)(buf))
+        #define le32(buf) _byteswap_ulong(*(uint32_t*)(buf))
+        #define le64(buf) _byteswap_uint64(*(uint64_t*)(buf))
     #else
         #define putle16(buf, x) (*(uint16_t*)(buf) = (uint16_t)(x))
         #define putle32(buf, x) (*(uint32_t*)(buf) = (uint32_t)(x))
         #define putle64(buf, x) (*(uint64_t*)(buf) = (uint64_t)(x))
+
+        #define readle16(fd, num) read((fd), &(num), 2)
+        #define readle32(fd, num) read((fd), &(num), 4)
+        #define readle64(fd, num) read((fd), &(num), 8)
+
+        #define le16(buf) (*(uint16_t*)(buf))
+        #define le32(buf) (*(uint32_t*)(buf))
+        #define le64(buf) (*(uint64_t*)(buf))
     #endif
 #else
     #ifdef WORDS_BIGENDIAN
         #define putle16(buf, x) (*(uint16_t*)(buf) = __builtin_bswap16((uint16_t)(x)))
         #define putle32(buf, x) (*(uint32_t*)(buf) = __builtin_bswap32((uint32_t)(x)))
         #define putle64(buf, x) (*(uint64_t*)(buf) = __builtin_bswap64((uint64_t)(x)))
+
+        #define readle16(fd, num) ((~read((fd), &(num), 2))?((num)=__builtin_bswap16((uint16_t)(num))):EOF)
+        #define readle32(fd, num) ((~read((fd), &(num), 4))?((num)=__builtin_bswap32((uint32_t)(num))):EOF)
+        #define readle64(fd, num) ((~read((fd), &(num), 8))?((num)=__builtin_bswap64((uint64_t)(num))):EOF)
+
+        #define le16(buf) __builtin_bswap16(*(uint16_t*)(buf))
+        #define le32(buf) __builtin_bswap32(*(uint32_t*)(buf))
+        #define le64(buf) __builtin_bswap64(*(uint64_t*)(buf))
     #else
         #define putle16(buf, x) (*(uint16_t*)(buf) = (uint16_t)(x))
         #define putle32(buf, x) (*(uint32_t*)(buf) = (uint32_t)(x))
         #define putle64(buf, x) (*(uint64_t*)(buf) = (uint64_t)(x))
+
+        #define readle16(fd, num) read((fd), &(num), 2)
+        #define readle32(fd, num) read((fd), &(num), 4)
+        #define readle64(fd, num) read((fd), &(num), 8)
+
+        #define le16(buf) (*(uint16_t*)(buf))
+        #define le32(buf) (*(uint32_t*)(buf))
+        #define le64(buf) (*(uint64_t*)(buf))
     #endif
 #endif
+
+#endif

include/page.h

@@ -0,0 +1,33 @@
+#ifndef _PAGE_H_
+#define _PAGE_H_
+
+#include <stdio.h>
+
+#ifndef PAGESZ
+    #define PAGESZ 4096
+#endif
+
+// 获取文件中的第一个空闲页，并将其 mmap 到内存
+// 如果现有空闲均无整页，则新分配一页
+// 返回：
+//    EOF 错误
+void* alloc_page(int fd);
+
+// 释放分配的页，将其标记为空闲以备使用
+// 返回：
+//    EOF 错误
+int free_page(int fd, void* page);
+
+// 获取文件中的第一个满足 size 大小的块
+// 返回：
+//    EOF 错误
+void* alloc_block(int fd, size_t size);
+
+// 释放块，并将其标记为空闲以备使用
+// 值得注意的是，只有在本页最后一块
+// 也被释放后，这一页才会被真正释放
+// 返回：
+//    EOF 错误
+int free_block(int fd, void* page);
+
+#endif

option.txt

@@ -0,0 +1 @@
+option(BUILD_TEST "Whether to build tests" OFF)

src/page.c

@@ -0,0 +1,38 @@
+// page.c
+// 管理文件中的空闲块
+
+#define _GNU_SOURCE /* See feature_test_macros(7) */
+
+#include <stdint.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/mman.h>
+
+#include "../include/binary.h"
+#include "../include/page.h"
+
+uint8_t nullpage[PAGESZ];
+
+void* alloc_page(int fd) {
+    uint64_t ptr, prev_ptr = 8;
+    void* page;
+    if(lseek(fd, 8, SEEK_SET) < 0) return EOF;
+    // 对于 page，只关心位于第一页 8~15 字节的 ptr of unused blk
+    readle64(fd, ptr);
+    while(ptr) {
+        if(!(ptr%PAGESZ)) { // 找到符合要求的页
+            page = mmap(NULL, PAGESZ, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, ptr);
+            if(page < 0) return page;
+            if(lseek(fd, prev_ptr, SEEK_SET) < 0) return EOF;
+            write(fd, page, 8); // 从空闲块链表移除本块
+            return page;
+        }
+        prev_ptr = ptr;
+        if(lseek(fd, ptr, SEEK_SET) < 0) return EOF;
+        readle64(fd, ptr);
+    }
+    ptr = lseek(fd, 0, SEEK_END);
+    if(ptr < 0 || !(ptr%PAGESZ)) return EOF;
+    if(write(fd, nullpage, PAGESZ) != PAGESZ) return EOF;
+    return mmap(NULL, PAGESZ, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, ptr);
+}

tests/binary_test.c

@@ -1,12 +1,41 @@
-#include "../src/binary.h"
+#include <unistd.h>
+#include <fcntl.h>
+#include "../include/binary.h"
 
 int main() {
-    char buf[8];
+    unsigned char buf[8];
     putle16(buf, 1);
-    if(buf[0] != 1) return 1;
-    putle32(buf, 2);
-    if(buf[0] != 2) return 2;
-    putle64(buf, 3);
-    if(buf[0] != 3) return 3;
+    if(buf[0] != 1 || le16(buf) != 0x01) return 1;
+    putle32(buf+1, 2);
+    if(buf[1] != 2 || le32(buf+1) != 0x02) return 2;
+    putle64(buf, 0xff0000);
+    if(buf[2] != 0xff || le64(buf) != 0xff0000) return 3;
+
+    int fd = open("binary_test_tmp.bin", O_WRONLY | O_CREAT | O_TRUNC, 0644);
+    if(fd < 0) {
+        perror("create");
+        return 4;
+    }
+    write(fd, "\001\002\003\004\005\006\a\b", 8);
+    close(fd);
+    fd = open("binary_test_tmp.bin", O_RDONLY | O_NONBLOCK);
+    if(fd < 0) {
+        perror("open");
+        return 5;
+    }
+    uint64_t ptr = 0;
+    readle16(fd, ptr);
+    printf("%04x\n", (uint16_t)ptr);
+    if((uint16_t)ptr != 0x0201) return 6;
+    lseek(fd, 0, SEEK_SET);
+    readle32(fd, ptr);
+    printf("%08x\n", (uint32_t)ptr);
+    if((uint32_t)ptr != 0x04030201) return 7;
+    lseek(fd, 0, SEEK_SET);
+    readle64(fd, ptr);
+    printf("%016llx\n", (uint64_t)ptr);
+    if((uint64_t)ptr != 0x0807060504030201) return 8;
+    close(fd);
+    remove("binary_test_tmp.bin");
     return 0;
 }