computing distances between planets

db.go

@@ -0,0 +1,100 @@
+package main
+
+import (
+	"database/sql"
+	_ "github.com/mattn/go-sqlite3"
+	"math"
+	"os"
+)
+
+func setupDb() {
+	db, err := sql.Open("sqlite3", "./exo.db")
+	if err != nil {
+		bail(E_No_DB, "unable to open database: %v", err)
+	}
+	defer db.Close()
+
+	stmnt := `create table if not exists planets (
+        id integer not null primary key autoincrement,
+        name text,
+        x integer,
+        y integer,
+        z integer,
+        planets integer
+    );`
+	_, err = db.Exec(stmnt)
+	if err != nil {
+		log_error("couldn't create table: %v", err)
+		return
+	}
+
+	n, err := countPlanets(db)
+	log_info("num planets: %v error: %v", n, err)
+	if n == 0 {
+		fi, err := os.Open(dataPath)
+		if err != nil {
+			bail(E_No_Data, "unable to open data path: %v", err)
+		}
+		c := make(chan exoSystem)
+		go speckStream(fi, c)
+		for planet := range c {
+			planet.Store(db)
+		}
+	}
+
+	idx := indexPlanets(db)
+	log_info("%v", idx)
+	fillEdges(db, idx)
+
+	stmnt = `create table if not exists edges (
+        id_1 integer,
+        id_2 integer,
+        distance real
+    );`
+	_, err = db.Exec(stmnt)
+	if err != nil {
+		log_error("couldn't create distance table: %v", err)
+		return
+	}
+
+}
+
+func sq(x float64) float64 {
+	return x * x
+}
+
+func dist3d(x1, y1, z1, x2, y2, z2 float64) float64 {
+	return math.Sqrt(sq(x1-x2) + sq(y1-y2) + sq(z1-z2))
+}
+
+func planetDistance(p1, p2 exoSystem) float64 {
+	return dist3d(p1.x, p1.y, p1.z, p2.x, p2.y, p2.z)
+}
+
+func indexPlanets(db *sql.DB) map[int]exoSystem {
+	rows, err := db.Query(`select * from planets`)
+	if err != nil {
+		log_error("unable to select all planets: %v", err)
+		return nil
+	}
+	defer rows.Close()
+	planets := make(map[int]exoSystem, 551)
+	for rows.Next() {
+		var id int
+		p := exoSystem{}
+		if err := rows.Scan(&id, &p.name, &p.x, &p.y, &p.z, &p.planets); err != nil {
+			log_info("unable to scan planet row: %v", err)
+			continue
+		}
+		planets[id] = p
+	}
+	return planets
+}
+
+func fillEdges(db *sql.DB, planets map[int]exoSystem) {
+	for i := 0; i < len(planets); i++ {
+		for j := i + 1; j < len(planets); j++ {
+			log_info("distance from %s to %s: %v", planets[i].name, planets[j].name, planetDistance(planets[i], planets[j]))
+		}
+	}
+}

errors.go

@@ -7,6 +7,7 @@ import (
 const (
 	E_Ok int = iota
 	E_No_Data
+    E_No_DB
 )
 
 type errorGroup []error

main.go

@@ -27,9 +27,5 @@ func bail(status int, template string, args ...interface{}) {
 }
 
 func main() {
-    fi, err := os.Open(dataPath)
-    if err != nil {
-        bail(E_No_Data, "unable to open data path: %v", err)
-    }
-    speckStream(fi)
+    setupDb()
 }

speck.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bufio"
+	"database/sql"
 	"fmt"
 	"io"
 	"regexp"
@@ -9,7 +10,8 @@ import (
 	"strings"
 )
 
-func speckStream(r io.ReadCloser) {
+func speckStream(r io.ReadCloser, c chan exoSystem) {
+	defer close(c)
 	defer r.Close()
 	keep := regexp.MustCompile(`^\s*[\d-]`)
 
@@ -28,7 +30,9 @@ func speckStream(r io.ReadCloser) {
 		if !keep.Match(line) {
 			continue
 		}
-		parseSpeckLine(line)
+		planet := parseSpeckLine(line)
+        c <- *planet
+
 	}
 }
 
@@ -38,11 +42,31 @@ type exoSystem struct {
 	name    string
 }
 
+func (e exoSystem) Store(db *sql.DB) {
+	_, err := db.Exec(`
+    insert into planets
+    (name, x, y, z, planets)
+    values
+    (?, ?, ?, ?, ?)
+    ;`, e.name, e.x, e.y, e.z, e.planets)
+    if err != nil {
+        log_error("%v", err)
+    }
+}
+
+func countPlanets(db *sql.DB) (int, error) {
+    row := db.QueryRow(`select count(*) from planets`)
+
+    var n int
+    err := row.Scan(&n)
+    return n, err
+}
+
 func (e exoSystem) String() string {
 	return fmt.Sprintf("<name: %s x: %v y: %v z: %v planets: %v>", e.name, e.x, e.y, e.z, e.planets)
 }
 
-func parseSpeckLine(line []byte) {
+func parseSpeckLine(line []byte) *exoSystem {
 	parts := strings.Split(string(line), " ")
 	var err error
 	var g errorGroup
@@ -62,5 +86,5 @@ func parseSpeckLine(line []byte) {
 	if g != nil {
 		log_error("%v", g)
 	}
-	log_info("%v", s)
+	return s
 }