piece-chain

commit 9b76662831fccb39c45ec4cc5e2223fe150a0fbd
Author: gearsix <gearsix@tuta.io>
Date:   Sat, 30 Apr 2022 13:39:24 +0100

git init; Piece, Buf, palloc, psplit, bufinit, bufidx.

Diffstat:
A
Makefile
 | 
8
++++++++
A
buf.c
 | 
91
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
buf.h
 | 
20
++++++++++++++++++++
A
test.c
 | 
88
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

4 files changed, 207 insertions(+), 0 deletions(-)
diff --git a/Makefile b/Makefile
@@ -0,0 +1,8 @@
+SRC := buf.c
+OUT := ec
+OPTS := -g -Wall -Wpedantic -std=c89
+
+all:
+	${CC} $(OPTS) $(SRC) main.c -o $(OUT)
+test:
+	${CC} $(OPTS) $(SRC) test.c -o $(OUT)
diff --git a/buf.c b/buf.c
@@ -0,0 +1,91 @@
+
+#include "buf.h"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+Piece *palloc()
+{
+	static Piece *pieceblk = NULL;
+	static size_t nblk = 0, npieces = 0;
+	static const size_t blksiz = BUFSIZ/sizeof(Piece);
+
+	if (npieces + 1 > blksiz * nblk)
+		pieceblk = realloc(pieceblk, (++nblk * blksiz) * sizeof(Piece));
+	if (!pieceblk) { perror("failed to allocate pieceblk memory"); exit(1); }
+	return &pieceblk[npieces++];
+}
+
+Piece *psplit(Piece *p, long int offset)
+{
+	Piece *q = palloc();
+	if (offset > 0) {
+		memcpy(q, p, sizeof(Piece));
+
+		q->off += offset;
+		q->len -= p->len = offset;
+		q->next = p->next;
+		q->prev = p;
+		p->next = q->next->prev =q;
+
+		p = q;
+	}
+	return p;
+}
+
+struct Buf *bufinit(const char *fpath)
+{
+	Buf *b = calloc(1, sizeof(Buf));
+	
+	b->append = tmpfile();
+
+	b->pos = palloc();
+	b->pos->prev = b->tail = palloc();
+	b->pos->next = b->head = palloc();
+	b->head->prev = b->tail->next = b->pos;
+
+	if (fpath) {
+		b->read = fopen(fpath, "rb");
+		if (ferror(b->read)) perror(fpath);
+		
+		b->pos->f = b->read;
+		fseek(b->read, 0, SEEK_END);
+		b->size = b->pos->len = ftell(b->read);
+	}
+
+	return b;
+}
+
+Piece *bufidx(Buf *b, size_t pos)
+{
+	size_t idx = b->idx, offset;
+	Piece *p = b->pos;
+
+	if (pos >= idx) {
+		while (pos >= idx + p->len && p->next) {
+			idx += p->len;
+			p = p->next;
+		}
+	} else {
+		do {
+			p = p->prev;
+			idx -= p->len;
+		} while(pos > idx && p->prev);
+	}
+
+	if (idx == pos) {
+		b->idx = idx;
+		b->pos = p;
+	} else {
+		offset = (idx >= pos) ? idx - pos : pos - idx;
+		b->pos = psplit(p, offset);
+		b->idx = pos;
+	}
+
+	return b->pos;
+}
+
+void bufins(Buf *b, size_t pos, const char *buf)
+{
+}
diff --git a/buf.h b/buf.h
@@ -0,0 +1,20 @@
+/* TODO */
+#include <stdio.h>
+
+typedef struct Piece {
+	FILE *f;
+	size_t off, len;
+	
+	struct Piece *undo, *redo;
+	struct Piece *prev, *next;
+} Piece;
+
+typedef struct Buf {
+	FILE *read, *append;
+	size_t size, idx;
+	struct Piece *tail, *pos, *head;
+} Buf;
+
+Buf *bufinit(const char *fpath);
+
+Piece *bufidx(Buf *b, size_t pos);
diff --git a/test.c b/test.c
@@ -0,0 +1,88 @@
+#include "buf.h"
+#include <stdio.h>
+#include <assert.h>
+#include <string.h>
+
+#define INFILE    "in.txt"
+#define INBUF     "hello world"
+#define OUTFILE "out.txt"
+#define OUTBUF "hey buddy!" /* tests will aim to change INBUF to this */
+
+Buf *b;
+
+void setup()
+{	
+	FILE *in = fopen(INFILE, "w+b");
+	if (ferror(in)) perror("fopen in.txt");
+	fputs(INBUF, in);
+	fclose(in);
+
+	return;
+}
+
+void print(Buf *b)
+{
+	Piece *p;
+
+	printf("b->tail: %p\tb->pos: %p\tb->head: %p\n\n",
+		(void *)b->tail, (void *)b->pos, (void *)b->head);
+
+	for (p = b->tail; p != NULL; p = p->next)
+		printf("%p\n", (void *)p);
+}
+
+void test_bufinit()
+{
+	Piece *p;
+	b = bufinit(INFILE);
+
+	assert(b->read);
+	assert(b->append);
+
+	p = b->tail;
+	assert(p);
+	assert(p->f == NULL);
+	assert(p->off == 0);
+	assert(p->len == 0);
+	assert(p->next == b->pos);
+	assert(p->prev == NULL);
+
+	p = b->pos;
+	assert(p);
+	assert(p->f == b->read);
+	assert(p->off == 0);
+	assert(p->len == strlen(INBUF));
+	assert(p->prev == b->tail);
+	assert(p->next == b->head);
+
+	p = b->head;
+	assert(p);
+	assert(p);
+	assert(p->f == NULL);
+	assert(p->off == 0);
+	assert(p->len == 0);
+	assert(p->next == NULL);
+	assert(p->prev == b->pos);
+}
+
+void test_bufidx()
+{
+	Piece *p; size_t idx = 5;
+	p = bufidx(b, idx);
+
+	assert(p == b->pos);
+	assert(p->f == b->read);
+	assert(p->off == idx);
+	assert(p->len == strlen(INBUF) - idx);
+	assert(p->prev != b->tail);
+	assert(p->next == b->head);
+}
+
+int main()
+{
+	setup();
+	test_bufinit();
+	test_bufidx();
+	puts("success - no assertions failed");
+	return 0;
+}