Float to string conversion implemented, excluding the case of range

without printable exponent (i.e. 10e-3 ... 10e7)

teavm-classlib/src/main/java/org/teavm/classlib/java/lang/StringBuilderTests.java

@@ -1,6 +1,6 @@
 package org.teavm.classlib.java.lang;
 
-import static org.junit.Assert.*;
+import static org.junit.Assert.assertEquals;
 import org.junit.Test;
 
 /**
@@ -64,6 +64,76 @@ public class StringBuilderTests {
         assertEquals("9223372036854775807", sb.toString());
     }
 
+    @Test
+    public void floatAppended() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(1.234E25F);
+        assertEquals("1.234E25", sb.toString());
+    }
+
+    @Test
+    public void floatAppended2() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(9.8765E30F);
+        assertEquals("9.8765E30", sb.toString());
+    }
+
+    @Test
+    public void negativeFloatAppended() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(-1.234E25F);
+        assertEquals("-1.234E25", sb.toString());
+    }
+
+    @Test
+    public void negativeFloatAppended2() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(9.8765E30F);
+        assertEquals("9.8765E30", sb.toString());
+    }
+
+    @Test
+    public void maxFloatAppended() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(3.402823E38f);
+        assertEquals("3.402823E38", sb.toString());
+    }
+
+    @Test
+    public void smallFloatAppended() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(1.234E-25F);
+        assertEquals("1.234E-25", sb.toString());
+    }
+
+    @Test
+    public void smallFloatAppended2() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(9.8764E-30F);
+        assertEquals("9.8764E-30", sb.toString());
+    }
+
+    @Test
+    public void negativeSmallFloatAppended() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(-1.234E-25F);
+        assertEquals("-1.234E-25", sb.toString());
+    }
+
+    @Test
+    public void negativeSmallFloatAppended2() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(-9.8764E-30F);
+        assertEquals("-9.8764E-30", sb.toString());
+    }
+
+    @Test
+    public void minFloatAppended() {
+        StringBuilder sb = new StringBuilder();
+        sb.append(1.175494E-38f);
+        assertEquals("1.175494E-38", sb.toString());
+    }
+
     @Test
     public void appendsCodePoint() {
         StringBuilder sb = new StringBuilder();

teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TAbstractStringBuilder.java

@@ -2,6 +2,7 @@ package org.teavm.classlib.java.lang;
 
 import org.teavm.classlib.java.lang.io.TSerializable;
 import org.teavm.classlib.java.util.TArrays;
+import org.teavm.javascript.ni.Remove;
 import org.teavm.javascript.ni.Rename;
 
 /**
@@ -9,6 +10,8 @@ import org.teavm.javascript.ni.Rename;
  * @author Alexey Andreev
  */
 class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequence {
+    private static float[] powersOfTen = { 1E1f, 1E2f, 1E4f, 1E8f, 1E16f, 1E32f };
+    private static float[] negPowersOfTen = { 1E-1f, 1E-2f, 1E-4f, 1E-8f, 1E-16f, 1E-32f };
     char[] buffer;
     int length;
 
@@ -104,6 +107,78 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
         return this;
     }
 
+    protected TAbstractStringBuilder append(float value) {
+        boolean negative = false;
+        int sz = 10;
+        if (value < 0) {
+            negative = true;
+            value = -value;
+            ++sz;
+        }
+        int exp = 0;
+        if (value > 1) {
+            int bit = 32;
+            exp = 0;
+            float digit = 1;
+            for (int i = powersOfTen.length - 1; i >= 0; --i) {
+                if ((exp | bit) <= 38 && powersOfTen[i] * digit < value) {
+                    digit *= powersOfTen[i];
+                    exp |= bit;
+                }
+                bit >>= 1;
+            }
+            value /= digit;
+        } else {
+            int bit = 32;
+            exp = 0;
+            float digit = 1;
+            for (int i = negPowersOfTen.length - 1; i >= 0; --i) {
+                if ((exp | bit) <= 38 && negPowersOfTen[i] * digit * 10 > value) {
+                    digit *= negPowersOfTen[i];
+                    exp |= bit;
+                }
+                bit >>= 1;
+            }
+            value /= digit;
+            exp = -exp;
+            ++sz;
+        }
+        value += 5E-7F;
+        if (exp > 10) {
+            ++sz;
+        }
+        ensureCapacity(length + sz);
+        if (negative) {
+            buffer[length++] = '-';
+        }
+        int intDigit = (int)value;
+        buffer[length++] = (char)('0' + intDigit);
+        buffer[length++] = '.';
+        value = (value - intDigit) * 10;
+        int zeros = 0;
+        for (int i = 0; i < 6; ++i) {
+            intDigit = (int)value;
+            if (intDigit == 0) {
+                ++zeros;
+            } else {
+                zeros = 0;
+            }
+            buffer[length++] = (char)('0' + intDigit);
+            value = (value - intDigit) * 10;
+        }
+        length -= Math.min(zeros, 5);
+        buffer[length++] = 'E';
+        if (exp < 0) {
+            exp = -exp;
+            buffer[length++] = '-';
+        }
+        if (exp > 10) {
+            buffer[length++] = (char)('0' + exp / 10);
+        }
+        buffer[length++] = (char)('0' + exp % 10);
+        return this;
+    }
+
     protected TAbstractStringBuilder append(char c) {
         ensureCapacity(length + 1);
         buffer[length++] = c;
@@ -134,6 +209,12 @@ class TAbstractStringBuilder extends TObject implements TSerializable, TCharSequ
         return new TString(buffer, 0, length);
     }
 
+    @Remove
+    @Override
+    public String toString() {
+        return new String(buffer, 0, length);
+    }
+
     @Override
     public int length() {
         return length;

teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java

@@ -423,6 +423,10 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
         return new TStringBuilder().append(l).toString0();
     }
 
+    public static TString valueOf(float f) {
+        return new TStringBuilder().append(f).toString0();
+    }
+
     @Override
     public boolean equals(TObject other) {
         if (this == other) {

teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TStringBuilder.java

@@ -23,6 +23,12 @@ public class TStringBuilder extends TAbstractStringBuilder {
         return this;
     }
 
+    @Override
+    public TStringBuilder append(float value) {
+        super.append(value);
+        return this;
+    }
+
     @Override
     public TStringBuilder append(char c) {
         super.append(c);