diff --git a/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexFile.java b/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexFile.java
index 3a8d58f8..7d697f1f 100644
--- a/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexFile.java
+++ b/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexFile.java
@@ -31,14 +31,43 @@
 
 package org.jf.dexlib2.dexbacked;
 
+import org.jf.util.ExceptionWithContext;
+
 import javax.annotation.Nullable;
 
 public class DexFile {
+    // TODO: consider using a direct ByteBuffer instead
+    protected final byte[] buf;
+
+    public DexFile(byte[] buf) {
+        this.buf = buf;
+    }
+
+    public String getString(int stringIndex) {
+        return null;
+    }
+
+    public int getFieldIdItemOffset(int fieldIndex) {
+        return 0;
+    }
+
+    public int getMethodIdItemOffset(int methodIndex) {
+        return 0;
+    }
+
+    public int getProtoIdItemOffset(int methodIndex) {
+        return 0;
+    }
+
     public String getType(int typeIndex) {
         return null;
     }
 
-    public String getString(int stringIndex) {
+    public String getField(int fieldIndex) {
+        return null;
+    }
+
+    public String getMethod(int methodIndex) {
         return null;
     }
 
@@ -47,20 +76,61 @@ public class DexFile {
         return null;
     }
 
-    public int getFieldIdItemOffset(int fieldIndex) {
-        return 0;
-    }
-
-    public int readSmallUleb128(int offset) {
-        return 0;
+    public String getReference(int referenceType, int referenceIndex) {
+        return null;
     }
 
     public int readSmallUint(int offset) {
-        return 0;
+        byte[] buf = this.buf;
+        int result = (buf[offset] & 0xff) |
+                     ((buf[offset+1] & 0xff) << 8) |
+                     ((buf[offset+2] & 0xff) << 16) |
+                     ((buf[offset+3] & 0xff) << 24);  // TODO: can get rid of last & 0xff?
+        if (result < 0) {
+            throw new ExceptionWithContext("Encountered uint that is out of range at offset 0x%x", offset);
+        }
+        return result;
     }
 
     public int readUshort(int offset) {
-        return 0;
+        byte[] buf = this.buf;
+        return (buf[offset] & 0xff) |
+               ((buf[offset+1] & 0xff) << 8);
+    }
+
+    public int readUbyte(int offset) {
+        return buf[offset] & 0xff;
+    }
+
+    public long readLong(int offset) {
+        // TODO: use | or +?
+        byte[] buf = this.buf;
+        return (buf[offset] & 0xffL) |
+               ((buf[offset+1] & 0xff) << 8) |
+               ((buf[offset+2] & 0xff) << 16) |
+               ((buf[offset+3] & 0xff) << 24) |
+               ((buf[offset+4] & 0xffL) << 32) |
+               ((buf[offset+5] & 0xffL) << 40) |
+               ((buf[offset+6] & 0xffL) << 48) |
+               (((long)buf[offset+7]) << 56);
+    }
+
+    public int readInt(int offset) {
+        byte[] buf = this.buf;
+        return (buf[offset] & 0xff) |
+               ((buf[offset+1] & 0xff) << 8) |
+               ((buf[offset+2] & 0xff) << 16) |
+               (buf[offset+3] << 24);
+    }
+
+    public int readShort(int offset) {
+        byte[] buf = this.buf;
+        return (buf[offset] & 0xff) |
+               (buf[offset+1] << 8);
+    }
+
+    public int readByte(int offset) {
+        return buf[offset];
     }
 
     public DexFileReader readerAt(int offset) {
diff --git a/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexFileReader.java b/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexFileReader.java
index ca44eb77..b8198141 100644
--- a/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexFileReader.java
+++ b/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/DexFileReader.java
@@ -31,150 +31,418 @@
 
 package org.jf.dexlib2.dexbacked;
 
+import org.jf.util.ExceptionWithContext;
+
 import javax.annotation.Nonnull;
 
 public class DexFileReader {
-    public DexFileReader(DexFile dexFile, int offset) {
+    @Nonnull private final DexFile dexFile;
+    private int offset;
+
+    public DexFileReader(@Nonnull DexFile dexFile, int offset) {
+        this.dexFile = dexFile;
+        this.offset = offset;
     }
 
-    @Nonnull
-    public DexFile getDexFile() {
-        return null;
-    }
+    @Nonnull public DexFile getDexFile() { return dexFile; }
+    public int getOffset() { return offset; }
 
-    public int getOffset() {
-        return 0;
-    }
-
-    public String getString(int stringIndex) {
-        return null;
-    }
-
-    public int getFieldIdItemOffset(int fieldIndex) {
-        return 0;
-    }
-
-    public int getMethodIdItemOffset(int methodIndex) {
-        return 0;
-    }
-
-    public int getProtoIdItemOffset(int methodIndex) {
-        return 0;
-    }
-
-    public String getType(int typeIndex) {
-        return null;
-    }
-
-    public String getField(int fieldIndex) {
-        return null;
-    }
-
-    public String getMethod(int fieldIndex) {
-        return null;
-    }
-
-    public String getReference(int referenceType, int referenceIndex) {
-        return null;
-    }
+    public String getString(int stringIndex) { return dexFile.getString(stringIndex); }
+    public int getFieldIdItemOffset(int fieldIndex) { return dexFile.getFieldIdItemOffset(fieldIndex); }
+    public int getMethodIdItemOffset(int methodIndex) { return dexFile.getMethodIdItemOffset(methodIndex); }
+    public int getProtoIdItemOffset(int methodIndex) { return dexFile.getProtoIdItemOffset(methodIndex); }
+    public String getType(int typeIndex) { return dexFile.getType(typeIndex); }
+    public String getField(int fieldIndex) { return dexFile.getField(fieldIndex); }
+    public String getMethod(int methodIndex) { return dexFile.getMethod(methodIndex); }
+    public String getReference(int type, int index) { return dexFile.getReference(type, index); }
 
+    /** {@inheritDoc} */
     public int readSleb128() {
-        return 0;
+        int end = offset;
+        int currentByteValue;
+        int result;
+        byte[] buf = dexFile.buf;
+
+        result = buf[end++] & 0xff;
+        if (result <= 0x7f) {
+            result = (result << 25) >> 25;
+        } else {
+            currentByteValue = buf[end++] & 0xff;
+            result = (result & 0x7f) | ((currentByteValue & 0x7f) << 7);
+            if (currentByteValue <= 0x7f) {
+                result = (result << 18) >> 18;
+            } else {
+                currentByteValue = buf[end++] & 0xff;
+                result |= (currentByteValue & 0x7f) << 14;
+                if (currentByteValue <= 0x7f) {
+                    result = (result << 11) >> 11;
+                } else {
+                    currentByteValue = buf[end++] & 0xff;
+                    result |= (currentByteValue & 0x7f) << 21;
+                    if (currentByteValue <= 0x7f) {
+                        result = (result << 4) >> 4;
+                    } else {
+                        currentByteValue = buf[end++] & 0xff;
+                        if (currentByteValue > 0x0f) {
+                            throw new ExceptionWithContext(
+                                    "Invalid sleb128 integer encountered at offset 0x%x", offset);
+                        }
+                        result |= currentByteValue << 28;
+                    }
+                }
+            }
+        }
+
+        offset = end;
+        return result;
     }
 
     public int readSmallUleb128() {
-        return 0;
+        int end = offset;
+        int currentByteValue;
+        int result;
+        byte[] buf = dexFile.buf;
+
+        result = buf[end++] & 0xff;
+        if (result > 0x7f) {
+            currentByteValue = buf[end++] & 0xff;
+            result = (result & 0x7f) | ((currentByteValue & 0x7f) << 7);
+            if (currentByteValue > 0x7f) {
+                currentByteValue = buf[end++] & 0xff;
+                result |= (currentByteValue & 0x7f) << 14;
+                if (currentByteValue > 0x7f) {
+                    currentByteValue = buf[end++] & 0xff;
+                    result |= (currentByteValue & 0x7f) << 21;
+                    if (currentByteValue > 0x7f) {
+                        currentByteValue = buf[end++] & 0xff;
+                        // we assume the most significant bit will never be set
+                        if (currentByteValue > 0x07) {
+                            if (currentByteValue <= 0x0f) {
+                                throw new ExceptionWithContext(
+                                        "Encountered valid uleb128 that is out of range at offset 0x%x", offset);
+                            }
+                            throw new ExceptionWithContext(
+                                    "Invalid uleb128 integer encountered at offset 0x%x", offset);
+                        }
+                        result |= currentByteValue << 28;
+                    }
+                }
+            }
+        }
+
+        offset = end;
+        return result;
     }
 
     public void skipUleb128() {
+        int end = offset;
+        byte currentByteValue;
+        byte[] buf = dexFile.buf;
+
+        currentByteValue = buf[end++];
+        if (currentByteValue < 0) { // if the MSB is set
+            currentByteValue = buf[end++];
+            if (currentByteValue < 0) { // if the MSB is set
+                currentByteValue = buf[end++];
+                if (currentByteValue < 0) { // if the MSB is set
+                    currentByteValue = buf[end++];
+                    if (currentByteValue < 0) { // if the MSB is set
+                        currentByteValue = buf[end++];
+                        if (currentByteValue < 0 || currentByteValue > 0x0f) {
+                            throw new ExceptionWithContext(
+                                    "Invalid uleb128 integer encountered at offset 0x%x", offset);
+                        }
+                    }
+                }
+            }
+        }
+
+        offset = end;
     }
 
     public int readSmallUint() {
-        return 0;
+        int o = offset;
+        int result = dexFile.readSmallUint(o);
+        offset = o + 4;
+        return result;
     }
 
     public int readUshort() {
-        return 0;
+        int o = offset;
+        int result = dexFile.readUshort(offset);
+        offset = o + 2;
+        return result;
     }
 
     public int readUbyte() {
-        // returns an int between 0 and 255
-        return 0;
-    }
-
-    public int readByte() {
-        // returns an int between -128 and 127
-        return 0;
-    }
-
-    public int readUshort(int offset) {
-        return 0;
-    }
-
-    public int readShort() {
-        return 0;
-    }
-
-    public int readSizedInt(int bytes) {
-        // bytes must be from 1 to 4. reads and interprets that many bytes as a little-endian sign-extended integer
-        return 0;
-    }
-
-    public int readSizedSmallUint(int bytes) {
-        // bytes must be from 1 to 4. reads and interprets that many bytes as a little-endian zero-extended integer
-        return 0;
-    }
-
-    public int readSizedRightExtendedUint(int bytes) {
-        // bytes must be from 1 to 4. reads and interprets that many bytes as a little-endian zero-right-extended
-        // integer
-        return 0;
-    }
-
-    public int readSizedRightExtendedUlong(int bytes) {
-        // bytes must be from 1 to 8. reads and interprets that many bytes as a little-endian zero-right-extended
-        // long
-        return 0;
-    }
-
-    public long readSizedLong(int bytes) {
-        // bytes must be from 1 to 8. reads and interprets that many bytes as a little-endian sign-extended long
-        return 0;
-    }
-
-    public long readSizedUlong(int bytes) {
-        // bytes must be from 1 to 8. reads and interprets that many bytes as a little-endian zero-extended long
-        return 0;
-    }
-
-    public int readSmallUint(int offset) {
-        return 0;
-    }
-
-    public int readInt() {
-        return 0;
+        int o = offset;
+        int result = dexFile.readUbyte(offset);
+        offset = o + 1;
+        return result;
     }
 
     public long readLong() {
-        return 0;
+        int o = offset;
+        long result = dexFile.readLong(offset);
+        offset = o + 2;
+        return result;
     }
 
-
-
-    @Nonnull
-    public DexFileReader atAbsolute(int offset) {
-        return null;
+    public int readInt() {
+        int o = offset;
+        int result = dexFile.readInt(offset);
+        offset = o + 4;
+        return result;
     }
 
-    // returns copy of this DexFileReader
-    @Nonnull
-    public DexFileReader copy() {
-        return null;
+    public int readShort() {
+        int o = offset;
+        int result = dexFile.readShort(offset);
+        offset = o + 2;
+        return result;
     }
 
-    public void skipByte() {
+    public int readByte() {
+        int o = offset;
+        int result = dexFile.readByte(offset);
+        offset = o + 1;
+        return result;
     }
 
-    public void skipBytes(int i) {
+    public void skipByte() { offset++; }
+    public void skipBytes(int i) { offset += i; }
+
+    public int readSmallUint(int offset) { return dexFile.readSmallUint(offset); }
+    public int readUshort(int offset) { return dexFile.readUshort(offset); }
+    public int readUbyte(int offset) { return dexFile.readUbyte(offset); }
+    public long readLong(int offset) { return dexFile.readLong(offset); }
+    public int readInt(int offset) { return dexFile.readInt(offset); }
+    public int readShort(int offset) { return dexFile.readShort(offset); }
+    public int readByte(int offset) { return dexFile.readByte(offset); }
+
+
+    public int readSizedInt(int bytes) {
+        int o = offset;
+        byte[] buf = dexFile.buf;
+
+        int result;
+        switch (bytes) {
+            case 4:
+                result = (buf[o] & 0xff) |
+                         ((buf[o+1] & 0xff) << 8) |
+                         ((buf[o+2] & 0xff) << 16) |
+                         (buf[o+3] << 24);
+                break;
+            case 3:
+                result = (buf[o] & 0xff) |
+                        ((buf[o+1] & 0xff) << 8) |
+                        ((buf[o+2]) << 16);
+                break;
+            case 2:
+                result = (buf[o] & 0xff) |
+                        ((buf[o+1]) << 8);
+                break;
+            case 1:
+                result = buf[o];
+                break;
+            default:
+                throw new ExceptionWithContext("Invalid size %d for sized int at offset 0x%x", bytes, offset);
+        }
+        offset = o + bytes;
+        return result;
+    }
+
+    public int readSizedSmallUint(int bytes) {
+        int o = offset;
+        byte[] buf = dexFile.buf;
+
+        int result = 0;
+        switch (bytes) {
+            case 4:
+                int b = buf[o+3];
+                if (b < 0) {
+                    throw new ExceptionWithContext(
+                            "Encountered valid sized uint that is out of range at offset 0x%x", offset);
+                }
+                result = (b & 0xff) << 24;
+                // fall-through
+            case 3:
+                result |= (buf[o+2] & 0xff) << 16;
+                // fall-through
+            case 2:
+                result |= (buf[o+1] & 0xff) << 8;
+                // fall-through
+            case 1:
+                result |= (buf[o] & 0xff);
+                break;
+            default:
+                throw new ExceptionWithContext("Invalid size %d for sized uint at offset 0x%x", bytes, offset);
+        }
+        offset = o + bytes;
+        return result;
+    }
+
+    public int readSizedRightExtendedInt(int bytes) {
+        int o = offset;
+        byte[] buf = dexFile.buf;
+
+        int result = 0;
+        switch (bytes) {
+            case 4:
+                result = (buf[o] & 0xff) |
+                         ((buf[o+1] & 0xff) << 8) |
+                         ((buf[o+2] & 0xff) << 16) |
+                         (buf[o+3] << 24);
+                break;
+            case 3:
+                result = (buf[o] & 0xff) << 8 |
+                         ((buf[o+1] & 0xff) << 16) |
+                         (buf[o+2] << 24);
+                break;
+            case 2:
+                result = (buf[o] & 0xff) << 16 |
+                         (buf[o+1] << 24);
+                break;
+            case 1:
+                result = buf[o] << 24;
+                break;
+            default:
+                throw new ExceptionWithContext(
+                        "Invalid size %d for sized, right extended int at offset 0x%x", bytes, offset);
+        }
+        offset = o + bytes;
+        return result;
+    }
+
+    public long readSizedRightExtendedLong(int bytes) {
+        int o = offset;
+        byte[] buf = dexFile.buf;
+
+        long result = 0;
+        switch (bytes) {
+            case 8:
+                result = (buf[o] & 0xff) |
+                         ((buf[o+1] & 0xff) << 8) |
+                         ((buf[o+2] & 0xff) << 16) |
+                         ((buf[o+3] & 0xff) << 24) |
+                         ((buf[o+4] & 0xffL) << 32) |
+                         ((buf[o+5] & 0xffL) << 40) |
+                         ((buf[o+6] & 0xffL) << 48) |
+                         (((long)buf[o+7]) << 56);
+                break;
+            case 7:
+                result = ((buf[o] & 0xff)) << 8 |
+                         ((buf[o+1] & 0xff) << 16) |
+                         ((buf[o+2] & 0xff) << 24) |
+                         ((buf[o+3] & 0xffL) << 32) |
+                         ((buf[o+4] & 0xffL) << 40) |
+                         ((buf[o+5] & 0xffL) << 48) |
+                         (((long)buf[o+6]) << 56);
+                break;
+            case 6:
+                result = ((buf[o] & 0xff)) << 16 |
+                         ((buf[o+1] & 0xff) << 24) |
+                         ((buf[o+2] & 0xffL) << 32) |
+                         ((buf[o+3] & 0xffL) << 40) |
+                         ((buf[o+4] & 0xffL) << 48) |
+                         (((long)buf[o+5]) << 56);
+                break;
+            case 5:
+                result = ((buf[o] & 0xff)) << 24 |
+                         ((buf[o+1] & 0xffL) << 32) |
+                         ((buf[o+2] & 0xffL) << 40) |
+                         ((buf[o+3] & 0xffL) << 48) |
+                         (((long)buf[o+4]) << 56);
+                break;
+            case 4:
+                result = ((buf[o] & 0xffL)) << 32 |
+                         ((buf[o+1] & 0xffL) << 40) |
+                         ((buf[o+2] & 0xffL) << 48) |
+                         (((long)buf[o+3]) << 56);
+                break;
+            case 3:
+                result = ((buf[o] & 0xffL)) << 40 |
+                         ((buf[o+1] & 0xffL) << 48) |
+                         (((long)buf[o+2]) << 56);
+                break;
+            case 2:
+                result = ((buf[o] & 0xffL)) << 48 |
+                         (((long)buf[o+1]) << 56);
+                break;
+            case 1:
+                result = ((long)buf[o]) << 56;
+                break;
+            default:
+                throw new ExceptionWithContext(
+                        "Invalid size %d for sized, right extended long at offset 0x%x", bytes, offset);
+        }
+        offset = o + bytes;
+        return result;
+    }
+
+    public long readSizedLong(int bytes) {
+        int o = offset;
+        byte[] buf = dexFile.buf;
+
+        long result = 0;
+        switch (bytes) {
+            case 8:
+                result = (buf[o] & 0xff) |
+                         ((buf[o+1] & 0xff) << 8) |
+                         ((buf[o+2] & 0xff) << 16) |
+                         ((buf[o+3] & 0xff) << 24) |
+                         ((buf[o+4] & 0xffL) << 32) |
+                         ((buf[o+5] & 0xffL) << 40) |
+                         ((buf[o+6] & 0xffL) << 48) |
+                         (((long)buf[o+7]) << 56);
+                break;
+            case 7:
+                result = (buf[o] & 0xff) |
+                         ((buf[o+1] & 0xff) << 8) |
+                         ((buf[o+2] & 0xff) << 16) |
+                         ((buf[o+3] & 0xff) << 24) |
+                         ((buf[o+4] & 0xffL) << 32) |
+                         ((buf[o+5] & 0xffL) << 40) |
+                         ((long)(buf[o+6]) << 48);
+                break;
+            case 6:
+                result = (buf[o] & 0xff) |
+                         ((buf[o+1] & 0xff) << 8) |
+                         ((buf[o+2] & 0xff) << 16) |
+                         ((buf[o+3] & 0xff) << 24) |
+                         ((buf[o+4] & 0xffL) << 32) |
+                         ((long)(buf[o+5]) << 40);
+                break;
+            case 5:
+                result = (buf[o] & 0xff) |
+                         ((buf[o+1] & 0xff) << 8) |
+                         ((buf[o+2] & 0xff) << 16) |
+                         ((buf[o+3] & 0xff) << 24) |
+                         ((long)(buf[o+4]) << 32);
+                break;
+            case 4:
+                result = (buf[o] & 0xff) |
+                        ((buf[o+1] & 0xff) << 8) |
+                        ((buf[o+2] & 0xff) << 16) |
+                        (buf[o+3] << 24);
+                break;
+            case 3:
+                result = (buf[o] & 0xff) << 8 |
+                        ((buf[o+1] & 0xff) << 16) |
+                        (buf[o+2] << 24);
+                break;
+            case 2:
+                result = (buf[o] & 0xff) << 16 |
+                        (buf[o+1] << 24);
+                break;
+            case 1:
+                result = buf[o] << 24;
+                break;
+            default:
+                throw new ExceptionWithContext("Invalid size %d for sized long at offset 0x%x", bytes, offset);
+        }
+
+        o += bytes;
+        return result;
     }
 }
\ No newline at end of file
diff --git a/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/value/DexBackedEncodedValue.java b/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/value/DexBackedEncodedValue.java
index dc08ee92..dbe6178a 100644
--- a/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/value/DexBackedEncodedValue.java
+++ b/dexlib2/src/main/java/org/jf/dexlib2/dexbacked/value/DexBackedEncodedValue.java
@@ -66,11 +66,11 @@ public abstract class DexBackedEncodedValue {
                 case ValueType.FLOAT:
                     Preconditions.checkValueArg(valueArg, 3);
                     return new ImmutableFloatEncodedValue(Float.intBitsToFloat(
-                            reader.readSizedRightExtendedUint(valueArg + 1)));
+                            reader.readSizedRightExtendedInt(valueArg + 1)));
                 case ValueType.DOUBLE:
                     Preconditions.checkValueArg(valueArg, 7);
                     return new ImmutableDoubleEncodedValue(Double.longBitsToDouble(
-                            reader.readSizedRightExtendedUlong(valueArg + 1)));
+                            reader.readSizedRightExtendedLong(valueArg + 1)));
                 case ValueType.STRING:
                     Preconditions.checkValueArg(valueArg, 3);
                     return new ImmutableStringEncodedValue(reader.getString(reader.readSizedSmallUint(valueArg + 1)));