amp

commit a8e7ed87318a9b388a7866741175b89d00776f48
parent 890d073d9da414458d62f5aaca7509b299f5b9c1
Author: Pavel Renev <an2qzavok@gmail.org>
Date:   Sun, 11 Feb 2024 17:53:30 +0000

start implementing separate fs backend

Diffstat:
A
fs.c
 | 
133
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
M
mkfile
 | 
9
+++++----
A
pages.c
 | 
88
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
A
pages.h
 | 
29
+++++++++++++++++++++++++++++

4 files changed, 255 insertions(+), 4 deletions(-)
diff --git a/fs.c b/fs.c
@@ -0,0 +1,133 @@
+#include <u.h>
+#include <libc.h>
+#include <fcall.h>
+#include <thread.h>
+#include <9p.h>
+
+#include "pages.h"
+
+enum {
+	FrameSize = sizeof(s16int) * 2,
+};
+
+PBuf pg;
+
+struct {
+	int min;
+	int max;
+	char str[32];
+} sel;
+
+void fs_read(Req *r);
+void fs_write(Req *r);
+
+void normalize_sel(void);
+void update_selstr(void);
+
+Srv ampsrv = {
+	.read = fs_read,
+	.write = fs_write,
+	// .open/.create (???) for handling truncating
+};
+
+File *fdata, *fcut, *fctl; 
+
+void
+usage(void)
+{
+	fprint(2,"usage: %s\n", argv0);
+	threadexitsall("usage");
+}
+
+void
+threadmain(int argc, char **argv)
+{
+	ARGBEGIN {
+	case 'D':
+		chatty9p++;
+		break;
+	default: usage();
+	} ARGEND
+	if (argc != 0) usage();
+
+	update_selstr();
+
+	ampsrv.tree = alloctree("amp", "amp", DMDIR|0555, nil);
+	fdata = createfile(ampsrv.tree->root, "data", "amp", 0666, nil);
+	fcut = createfile(ampsrv.tree->root, "cut", "amp", 0666, nil);
+	fctl = createfile(ampsrv.tree->root, "ctl", "amp", 0666, nil);
+	threadpostmountsrv(&ampsrv, "amp", "/mnt/amp", MREPL);
+}
+
+void
+fs_read(Req *r)
+{
+	if (r->fid->file == fdata) {
+		r->ofcall.count = pbread(&pg, r->ofcall.data,
+		  r->ifcall.count, r->ifcall.offset);
+		respond(r, nil);
+	} else if (r->fid->file == fcut) {
+		respond(r, "fcut nope");
+	} else if (r->fid->file == fctl) {
+		readstr(r, sel.str);
+		respond(r, nil);
+	} else {
+		respond(r, "nope");
+	}
+}
+
+void
+fs_write(Req *r)
+{
+	if (r->fid->file == fdata) {
+		r->ofcall.count = pbwrite(&pg, r->ifcall.data,
+		  r->ifcall.count, r->ifcall.offset);
+		if (pg.count > fdata->length) fdata->length = pg.count;
+		respond(r, nil);
+	} else if (r->fid->file == fcut) {
+		respond(r, "fcut nope");
+	} else if (r->fid->file == fctl) {
+		int newmin, newmax;
+		char *np, *rp;
+		np = r->ifcall.data;
+		newmin = strtol(np, &rp, 10);
+		if (rp <= np) {
+			respond(r, "bad first value");
+			return;
+		}
+		newmax = strtol(rp, &rp, 10);
+		if (rp <= np) {
+			respond(r, "bad second value");
+			return;
+		}
+		if (rp - np > r->ifcall.count) {
+			respond(r, "somehow buffer overrun");
+			return;
+		}
+		sel.min = newmin;
+		sel.max = newmax;
+		normalize_sel();
+		update_selstr();
+		r->ofcall.count = r->ifcall.count;
+		respond(r, nil);
+	} else {
+		respond(r, "nope");
+	}
+}
+
+void
+normalize_sel(void)
+{
+	if (sel.min > sel.max) {
+		int x = sel.max;
+		sel.max = sel.min;
+		sel.min = x;
+	};
+	// TODO: should check max is not bigger than total buffer size
+}
+
+void
+update_selstr(void)
+{
+	snprint(sel.str, sizeof(sel.str), "%11d %11d ", sel.min, sel.max);
+}
diff --git a/mkfile b/mkfile
@@ -1,9 +1,10 @@
 </$objtype/mkfile
 
-TARG=amp
+TARG=fs
 
-OFILES=\
-	amp.$O\
+OFILES=pages.$O
+HFILES=pages.h
 
 BIN=/$objtype/bin
-</sys/src/cmd/mkone
+
+</sys/src/cmd/mkmany
diff --git a/pages.c b/pages.c
@@ -0,0 +1,88 @@
+#include <u.h>
+#include <libc.h>
+
+#include "pages.h"
+
+Page *
+allocpage(void)
+{
+	Page *new = mallocz(sizeof(Page), 1);
+	new->count = PageSize;
+	new->buf = mallocz(PageSize, 1);
+	return new;
+}
+
+long
+pbwrite(PBuf *pb, void *buf, long nbytes, vlong offset)
+{
+	Page *pgpt;
+	vlong page_offset = 0;
+	long n, nwritten = 0;
+	while (offset + nbytes > pb->size) {
+		addpage(pb);
+	}
+	pgpt = pb->start;
+	if (pb->count < offset + nbytes) pb->count = offset + nbytes;
+	while (nbytes > 0) {
+		assert(page_offset <= offset);
+		if (page_offset + pgpt->count > offset) {
+			n = page_offset + pgpt->count - offset;
+			if (n > nbytes) n = nbytes;
+			memcpy(pgpt->buf, buf, n);
+			nwritten += n;
+			buf = (char *)buf + n;
+			offset +=n;
+			nbytes -= n;
+		}
+		page_offset += pgpt->count;
+		pgpt = pgpt->next;
+	}
+	if (offset > pb->size) {
+		pb->size = offset;
+	}
+	return nwritten;
+}
+
+long
+pbread(PBuf *pb, void *buf, long nbytes, vlong offset)
+{
+	Page *pgpt = pb->start;
+	long n, nread = 0;
+	if (offset >= pb->count) nbytes = 0;
+	if (offset + nbytes >= pb->count) {
+		nbytes = (pb->count - offset);
+	}
+	while (nbytes > 0) {
+		if (pgpt == nil) {
+			break;
+		}
+		if (offset >= pgpt->count) {
+			offset -= pgpt->count;
+			pgpt = pgpt->next;
+			continue;
+		}
+		n = nbytes;
+		if (pgpt->count - offset < n) n = pgpt->count - offset;
+		memcpy(buf, pgpt->buf + offset, n);
+		nread += n;
+		buf = (char *)buf + n;
+		offset += n;
+		nbytes -= n;
+	}
+	return nread;
+}
+
+Page *
+addpage(PBuf *pb)
+{
+	Page *new = allocpage();
+	if (pb->start == nil) pb->start = new;
+	if (pb->end == nil) pb->end = new;
+	else {
+		new->prev = pb->end;
+		pb->end->next = new;
+		pb->end = new;
+	}
+	pb->size += new->count;
+	return new;
+}
diff --git a/pages.h b/pages.h
@@ -0,0 +1,29 @@
+// managing paginated memory buffers
+
+enum {
+	PageSize = 2048,
+};
+
+typedef struct Page Page;
+struct Page {
+	Page *prev;
+	Page *next;
+	vlong count;
+	char *buf;
+};
+
+Page *allocpage(void);
+
+typedef struct PBuf PBuf;
+struct PBuf {
+	Page *start;
+	Page *end;
+	vlong size; // how many bytes were allocated in total
+	vlong count; // how many bytes are used for storage
+	//              count <= size
+};
+
+long pbwrite(PBuf *pb, void *buf, long nbytes, vlong offset); 
+long pbread(PBuf *pb, void *buf, long nbytes, vlong offset);
+
+Page * addpage(PBuf *pb);