From fc2e066ca0cb3c861d3f80560ee862a735498e3b Mon Sep 17 00:00:00 2001
From: Giacomo Tesio <giacomo@tesio.it>
Date: Tue, 7 Nov 2017 00:52:05 +0100
Subject: [PATCH] cmd: import pstree from 9front

---
 sys/src/cmd/cmds.json |   1 +
 sys/src/cmd/pstree.c  | 184 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 185 insertions(+)
 create mode 100644 sys/src/cmd/pstree.c

diff --git a/sys/src/cmd/cmds.json b/sys/src/cmd/cmds.json
index 2194b31..a8b0f03 100644
--- a/sys/src/cmd/cmds.json
+++ b/sys/src/cmd/cmds.json
@@ -40,6 +40,7 @@
 			"p.c",
 			"pipefile.c",
 			"ps.c",
+			"pstree.c",
 			"pwd.c",
 			"ramfs.c",
 			"rm.c",
diff --git a/sys/src/cmd/pstree.c b/sys/src/cmd/pstree.c
new file mode 100644
index 0000000..8618095
--- /dev/null
+++ b/sys/src/cmd/pstree.c
@@ -0,0 +1,184 @@
+#include <u.h>
+#include <lib9.h>
+#include <bio.h>
+
+typedef struct Proc Proc;
+struct Proc {
+	int pid;
+	Proc *first, *parent, *next;
+	Proc *hash;
+};
+
+Proc	*hash[1024];
+Rune	buf[512];
+Biobuf	bout;
+
+Proc *
+getproc(int pid)
+{
+	Proc *p;
+
+	for(p = hash[pid % nelem(hash)]; p; p = p->hash)
+		if(p->pid == pid)
+			return p;
+	return nil;
+}
+
+void
+addproc(int pid)
+{
+	Proc *p;
+	
+	p = mallocz(sizeof(*p), 1);
+	if(p == nil)
+		sysfatal("malloc: %r");
+	p->pid = pid;
+	p->hash = hash[pid % nelem(hash)];
+	hash[pid % nelem(hash)] = p;
+}
+
+int
+theppid(int pid)
+{
+	char b[128];
+	int fd, ppid;
+	
+	ppid = 0;
+	snprint(b, sizeof(b), "%d/ppid", pid);
+	fd = open(b, OREAD);
+	if(fd >= 0){
+		memset(b, 0, sizeof b);
+		if(read(fd, b, sizeof b-1) >= 0){
+			ppid = atoi(b);
+			if(ppid < 0)
+				ppid = 0;
+		}
+		close(fd);
+	}
+	return ppid;
+}
+
+void
+addppid(int pid)
+{
+	Proc *p, *par, **l;
+	
+	p = getproc(pid);
+	par = getproc(theppid(pid));
+	if(par == nil)
+		par = getproc(0);
+	p->parent = par;
+	for(l = &par->first; *l; l = &((*l)->next))
+		if((*l)->pid > pid)
+			break;
+	p->next = *l;
+	*l = p;
+}
+
+void
+addprocs(void)
+{
+	int fd, rc, i;
+	Dir *d;
+	
+	fd = open(".", OREAD);
+	if(fd < 0)
+		sysfatal("open: %r");
+	rc = dirreadall(fd, &d);
+	if(rc < 0)
+		sysfatal("dirreadall: %r");
+	close(fd);
+	for(i = 0; i < rc; i++)
+		if(d[i].mode & DMDIR)
+			addproc(atoi(d[i].name));
+	for(i = 0; i < rc; i++)
+		if(d[i].mode & DMDIR)
+			addppid(atoi(d[i].name));
+	free(d);
+}
+
+int
+readout(char *file)
+{
+	int fd, rc, i, n;
+	char b[512];
+
+	fd = open(file, OREAD);
+	if(fd < 0)
+		return -1;
+	n = 0;
+	while((rc = read(fd, b, sizeof b)) > 0){
+		for(i=0; i<rc; i++)
+			if(b[i] == '\n')
+				b[i] = ' ';
+		n += Bwrite(&bout, b, rc);
+	}
+	close(fd);
+	return n;
+}
+
+void
+printargs(int pid)
+{
+	char b[128], *p;
+	int fd;
+
+	snprint(b, sizeof(b), "%d/args", pid);
+	if(readout(b) > 0)
+		return;
+	snprint(b, sizeof(b), "%d/status", pid);
+	fd = open(b, OREAD);
+	if(fd >= 0){
+		memset(b, 0, sizeof b);
+		if(read(fd, b, 27) > 0){
+			p = b + strlen(b);
+			while(p > b && p[-1] == ' ')
+				*--p = 0;
+			Bprint(&bout, "%s", b);
+		}
+		close(fd);
+	}
+}
+
+void
+descend(Proc *p, Rune *r)
+{
+	Rune last;
+	Proc *q;
+	
+	last = *--r;
+	*r = last == L' ' ? L'└' : L'├';
+	if(p->pid != 0){
+		Bprint(&bout, "%-11d %S", p->pid, buf);
+		printargs(p->pid);
+		Bprint(&bout, "\n");
+	}
+	*r = last;
+	*++r = L'│';
+	for(q = p->first; q; q = q->next) {
+		if(q->next == nil)
+			*r = L' ';
+		descend(q, r + 1);
+	}
+	*r = 0;
+}
+
+void
+printprocs(void)
+{
+	descend(getproc(0), buf);
+}
+
+void
+main()
+{
+	Binit(&bout, 1, OWRITE);
+	if(chdir("/proc")==-1)
+		sysfatal("chdir: %r");
+
+	addproc(0);
+	addprocs();
+	printprocs();
+
+	exits(0);
+}