first version

Homework10/2018202144NZM/Makefile

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+_zip: _zip.so main.c
+	gcc -o _zip main.c ./_zip.so 
+_zip.so: zip.c
+	gcc -shared -fPIC -o _zip.so zip.c
+clean:
+	rm -f _zip.so

Homework10/2018202144NZM/README.md

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+35% compression ratio
+wait to upgrade after I get off the train

Homework10/2018202144NZM/main.c

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+#include <stdio.h>
+#include "zip.h"
+
+int main()
+{
+	zip("zip.in", "x.zip");
+	decode("x.zip", "zip.out");
+	return 0;
+}

Homework10/2018202144NZM/zip.c

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+#include <stdio.h>
+#include <stdlib.h>
+#include "zip.h"
+
+#define DATA_SIZE 1000000
+#define MAX_DIS 32768
+#define SIZE_OF_CHAR 100000
+#define SIZE_OF_ASC 256
+#define INF 2e9
+
+#define swap(a,b) ((a)^=(b)^=(a)^=(b))
+
+struct pair
+{
+	int v;
+	int id;
+}char_cnt[SIZE_OF_CHAR], huff[SIZE_OF_ASC];
+
+struct edge
+{
+	int v, next;
+}e[DATA_SIZE];
+
+static unsigned char outhuff[DATA_SIZE] = {0};
+unsigned char zip_mp[SIZE_OF_CHAR] = {0}, inhuff[DATA_SIZE] = {0};
+int zip_size;
+static int n, head[DATA_SIZE], edge_cnt = 0;
+
+static void insert(int v1, int v2)
+{
+	e[++edge_cnt].v = v2;
+	e[edge_cnt].next = head[v1];
+	head[v1] = edge_cnt;
+}
+
+static void dfs(int x,int fa, int dep)
+{
+	int ch = 0;
+	for (int i = head[x]; i; i = e[i].next) {
+		dfs(e[i].v, x, (dep << 1) + ch);
+		ch++;
+	}
+	if (!head[x]) {
+		huff[x].v = dep;
+		huff[x].id = x;
+		zip_mp[dep] = x;
+	}
+}
+
+static int cmp(const void *v1, const void *v2)
+{
+	return ((struct pair *)v1)->v > ((struct pair *)v2)->v;	
+}
+
+void zip(char *filename, char *output)
+{
+	FILE *fp = fopen(filename, "r");
+	n = 0;
+	while (fread(inhuff + n, 1, 1, fp))
+		n++;
+	zip_size = n;
+	for (int i = 0; i < SIZE_OF_ASC; i++) {
+		char_cnt[i].id = i;
+		char_cnt[i].v = 0;
+	}
+	for (int i = 0; i < n; i++)
+		char_cnt[inhuff[i]].v++;
+	for (int i = 0; i < SIZE_OF_ASC; i++)
+		if (char_cnt[i].v == 0)
+			char_cnt[i].v = INF;
+	qsort(char_cnt, SIZE_OF_ASC, sizeof(struct pair), cmp);
+	int head = 0, asc_cnt = SIZE_OF_ASC;
+	int asc_size = SIZE_OF_ASC;
+	while (char_cnt[asc_size - 1].v == INF)
+		asc_size--;
+	while(head < asc_size - 1) {
+		insert(asc_cnt, char_cnt[head].id);
+		insert(asc_cnt, char_cnt[head + 1].id);
+		char_cnt[++head].id = asc_cnt;
+		char_cnt[head].v += char_cnt[head - 1].v;
+		for (int j = head; j < asc_size - 1; j++) {
+			if (char_cnt[j].v > char_cnt[j + 1].v) {
+				swap(char_cnt[j].id, char_cnt[j + 1].id);
+				swap(char_cnt[j].v, char_cnt[j + 1].v);
+			}
+			else 
+				break;
+		}
+		asc_cnt++;
+	}
+	int root = char_cnt[asc_size - 1].id;
+	dfs(root, 0, 0);
+	int out_cnt = 3, out_pos = 0;
+	for (int i = 0; i < n; i++) {
+		int flag = 0, v = huff[inhuff[i]].v;
+		for (int j = 3; j > 0; j--) {
+			if (v & (1 << j))
+				flag = 1;
+			if (flag) {
+				if (v & (1 << j))
+					outhuff[out_pos] += (1 << out_cnt);
+				out_cnt--;
+				if (out_cnt < 0) {
+					out_cnt = 3;
+					out_pos++;
+				}
+			}	
+		}
+	}
+	if (out_cnt != 3)
+		out_pos++;
+	fp = fopen(output, "w");
+	fwrite(outhuff, 1, out_pos, fp);
+}
+
+static char incode[DATA_SIZE] = {0};
+
+void decode(char *input, char *output)
+{
+	FILE *fp = fopen(input, "r");
+	FILE *fp2 = fopen(output, "w");
+	int n = 0;
+	while (fread(incode + n, 1, 1, fp))
+		n++;
+	int encode = 0, pos = -1, _pos = 3;
+	for (int i = 0; i < n; i++) {
+		if (i % 4 == 0)
+			pos++;
+		encode = (encode << 1);
+		if (incode[pos] & (1 << _pos))
+			encode++;
+		if (zip_mp[encode]) {
+			fputc(zip_mp[encode], fp2);
+			encode = 0;
+		}
+		_pos--;
+		_pos = (_pos + 4) % 4;
+	}
+	for (int i = 0; i < zip_size; i++)
+		fputc(inhuff[i], fp2);
+}

Homework10/2018202144NZM/zip.h

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+void zip(char *input_filename, char *output_filename);
+
+void decode(char *input_filename, char *output_filename);