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authorJuan Manuel Tomás <jtomas1815@gmail.com>2020-05-24 05:35:00 -0300
committerJuan Manuel Tomás <jtomas1815@gmail.com>2020-05-24 05:35:00 -0300
commit98280238383dc390207827d09dc92e0459229134 (patch)
treee2bc7c0877289165463dd6f9c2e77b570b22e29c /page.cpp
parentd37027bbd7ac13fdd0f1e2f01e1ec4b75b6c9588 (diff)
downloadjet-98280238383dc390207827d09dc92e0459229134.tar.gz
jet-98280238383dc390207827d09dc92e0459229134.zip
Rewrite in c++
Diffstat (limited to 'page.cpp')
-rw-r--r--page.cpp88
1 files changed, 88 insertions, 0 deletions
diff --git a/page.cpp b/page.cpp
new file mode 100644
index 0000000..7f56fc9
--- /dev/null
+++ b/page.cpp
@@ -0,0 +1,88 @@
+#include <stdint.h>
+#include <string.h>
+#include <stdlib.h>
+#include <assert.h>
+
+#ifndef PAGE_SIZE
+#define PAGE_SIZE 4096
+#endif
+
+struct Page {
+ uint8_t *elements;
+ Page *next;
+ Page *prev;
+ uint16_t gap_start;
+ uint16_t gap_end;
+ uint16_t element_count;
+
+ Page() {
+ elements = new uint8_t[PAGE_SIZE];
+ gap_start = 0;
+ gap_end = PAGE_SIZE;
+ element_count = 0;
+ next = nullptr;
+ prev = nullptr;
+ }
+
+ ~Page() {
+ if (prev) prev->next = next;
+ if (next) next->prev = prev;
+ delete[] elements;
+ }
+
+ void split() {
+ Page *front = new Page();
+
+ memcpy(front->elements, elements + PAGE_SIZE / 2, PAGE_SIZE / 2);
+
+ front->gap_start = PAGE_SIZE / 2;
+ front->gap_end = PAGE_SIZE;
+ front->element_count = PAGE_SIZE / 2;
+
+ gap_start = PAGE_SIZE / 2;
+ gap_end = PAGE_SIZE;
+ element_count = PAGE_SIZE / 2;
+
+ if (next) {
+ next->prev = front;
+ }
+ front->next = next;
+ front->prev = this;
+ next = front;
+ }
+
+ void copy_to(Page *dest) {
+ memcpy(dest->elements, elements, PAGE_SIZE);
+ dest->gap_start = gap_start;
+ dest->gap_end = gap_end;
+ dest->element_count = element_count;
+ }
+
+ void operator++(int) {
+ assert(gap_end < PAGE_SIZE);
+ elements[gap_start] = elements[gap_end];
+ gap_start++;
+ gap_end++;
+ }
+
+ void operator--(int) {
+ assert(gap_start > 0);
+ gap_end--;
+ gap_start--;
+ elements[gap_end] = elements[gap_start];
+ }
+
+ void push(uint8_t c) {
+ assert(element_count < PAGE_SIZE);
+ elements[gap_start] = c;
+ gap_start++;
+ element_count++;
+ }
+
+ void pop() {
+ assert(gap_start > 0);
+ gap_start--;
+ element_count--;
+ }
+
+};