nostrdb: port everything over to be in as sync as possible

for now

nostrdb/io.h

@@ -0,0 +1,48 @@
+
+#include <stdio.h>
+
+static int read_fd(FILE *fd, unsigned char *buf, int buflen, int *written)
+{
+	unsigned char *p = buf;
+	int len = 0;
+	*written = 0;
+
+	do {
+		len = fread(p, 1, 4096, fd);
+		*written += len;
+		p += len;
+		if (p > buf + buflen)
+			return 0;
+	} while (len == 4096);
+
+	return 1;
+}
+
+static int write_file(const char *filename, unsigned char *buf, int buflen)
+{
+	FILE *file = NULL;
+	int ok;
+
+	file = fopen(filename, "w");
+	if (file == NULL)
+		return 0;
+
+	ok = fwrite(buf, buflen, 1, file);
+	fclose(file);
+	return ok;
+}
+
+static int read_file(const char *filename, unsigned char *buf, int buflen, int *written)
+{
+	FILE *file = NULL;
+	int ok;
+
+	file = fopen(filename, "r");
+	if (file == NULL)
+		return 1;
+
+	ok = read_fd(file, buf, buflen, written);
+	fclose(file);
+	return ok;
+}
+