classreader.java

asm的源码包 并且包含英文的文档

                        case ClassWriter.FIELDORMETH_INSN:
                        case ClassWriter.TYPE_INSN:
                        case ClassWriter.IINC_INSN:
                            v += 3;
                            break;
                        case ClassWriter.ITFMETH_INSN:
                            v += 5;
                            break;
                        // case MANA_INSN:
                        default:
                            v += 4;
                            break;
                    }
                }
                // parses the try catch entries
                j = readUnsignedShort(v);
                v += 2;
                for (; j > 0; --j) {
                    label = readUnsignedShort(v);
                    Label start = labels[label];
                    if (start == null) {
                        labels[label] = start = new Label();
                    }
                    label = readUnsignedShort(v + 2);
                    Label end = labels[label];
                    if (end == null) {
                        labels[label] = end = new Label();
                    }
                    label = readUnsignedShort(v + 4);
                    Label handler = labels[label];
                    if (handler == null) {
                        labels[label] = handler = new Label();
                    }
                    int type = readUnsignedShort(v + 6);
                    if (type == 0) {
                        mv.visitTryCatchBlock(start, end, handler, null);
                    } else {
                        mv.visitTryCatchBlock(start,
                                end,
                                handler,
                                readUTF8(items[type], c));
                    }
                    v += 8;
                }
                // parses the local variable, line number tables, and code
                // attributes
                int varTable = 0;
                int varTypeTable = 0;
                int stackMap = 0;
                int frameCount = 0;
                int frameMode = 0;
                int frameOffset = 0;
                int frameLocalCount = 0;
                int frameLocalDiff = 0;
                int frameStackCount = 0;
                Object[] frameLocal = null;
                Object[] frameStack = null;
                boolean zip = true;
                cattrs = null;
                j = readUnsignedShort(v);
                v += 2;
                for (; j > 0; --j) {
                    attrName = readUTF8(v, c);
                    if (attrName.equals("LocalVariableTable")) {
                        if (!skipDebug) {
                            varTable = v + 6;
                            k = readUnsignedShort(v + 6);
                            w = v + 8;
                            for (; k > 0; --k) {
                                label = readUnsignedShort(w);
                                if (labels[label] == null) {
                                    labels[label] = new Label(true);
                                }
                                label += readUnsignedShort(w + 2);
                                if (labels[label] == null) {
                                    labels[label] = new Label(true);
                                }
                                w += 10;
                            }
                        }
                    } else if (attrName.equals("LocalVariableTypeTable")) {
                        varTypeTable = v + 6;
                    } else if (attrName.equals("LineNumberTable")) {
                        if (!skipDebug) {
                            k = readUnsignedShort(v + 6);
                            w = v + 8;
                            for (; k > 0; --k) {
                                label = readUnsignedShort(w);
                                if (labels[label] == null) {
                                    labels[label] = new Label(true);
                                }
                                labels[label].line = readUnsignedShort(w + 2);
                                w += 4;
                            }
                        }
                    } else if (attrName.equals("StackMapTable")) {
                        if ((flags & SKIP_FRAMES) == 0) {
                            stackMap = v + 8;
                            frameCount = readUnsignedShort(v + 6);
                        }
                        /*
                         * here we do not extract the labels corresponding to
                         * the attribute content. This would require a full
                         * parsing of the attribute, which would need to be
                         * repeated in the second phase (see below). Instead the
                         * content of the attribute is read one frame at a time
                         * (i.e. after a frame has been visited, the next frame
                         * is read), and the labels it contains are also
                         * extracted one frame at a time. Thanks to the ordering
                         * of frames, having only a "one frame lookahead" is not
                         * a problem, i.e. it is not possible to see an offset
                         * smaller than the offset of the current insn and for
                         * which no Label exist.
                         */
                        // TODO true for frame offsets,
                        // but for UNINITIALIZED type offsets?
                    } else if (attrName.equals("StackMap")) {
                        if ((flags & SKIP_FRAMES) == 0) {
                            stackMap = v + 8;
                            frameCount = readUnsignedShort(v + 6);
                            zip = false;
                        }
                        /*
                         * IMPORTANT! here we assume that the frames are
                         * ordered, as in the StackMapTable attribute, although
                         * this is not guaranteed by the attribute format.
                         */
                    } else {
                        for (k = 0; k < attrs.length; ++k) {
                            if (attrs[k].type.equals(attrName)) {
                                attr = attrs[k].read(this,
                                        v + 6,
                                        readInt(v + 2),
                                        c,
                                        codeStart - 8,
                                        labels);
                                if (attr != null) {
                                    attr.next = cattrs;
                                    cattrs = attr;
                                }
                            }
                        }
                    }
                    v += 6 + readInt(v + 2);
                }

                // 2nd phase: visits each instruction
                if (stackMap != 0) {
                    // creates the very first (implicit) frame from the method
                    // descriptor
                    frameLocal = new Object[maxLocals];
                    frameStack = new Object[maxStack];
                    if (unzip) {
                        int local = 0;
                        if ((access & Opcodes.ACC_STATIC) == 0) {
                            if (name.equals("<init>")) {
                                frameLocal[local++] = Opcodes.UNINITIALIZED_THIS;
                            } else {
                                frameLocal[local++] = readClass(header + 2, c);
                            }
                        }
                        j = 1;
                        loop: while (true) {
                            k = j;
                            switch (desc.charAt(j++)) {
                                case 'Z':
                                case 'C':
                                case 'B':
                                case 'S':
                                case 'I':
                                    frameLocal[local++] = Opcodes.INTEGER;
                                    break;
                                case 'F':
                                    frameLocal[local++] = Opcodes.FLOAT;
                                    break;
                                case 'J':
                                    frameLocal[local++] = Opcodes.LONG;
                                    break;
                                case 'D':
                                    frameLocal[local++] = Opcodes.DOUBLE;
                                    break;
                                case '[':
                                    while (desc.charAt(j) == '[') {
                                        ++j;
                                    }
                                    if (desc.charAt(j) == 'L') {
                                        ++j;
                                        while (desc.charAt(j) != ';') {
                                            ++j;
                                        }
                                    }
                                    frameLocal[local++] = desc.substring(k, ++j);
                                    break;
                                case 'L':
                                    while (desc.charAt(j) != ';') {
                                        ++j;
                                    }
                                    frameLocal[local++] = desc.substring(k + 1,
                                            j++);
                                    break;
                                default:
                                    break loop;
                            }
                        }
                        frameLocalCount = local;
                    }
                    /*
                     * for the first explicit frame the offset is not
                     * offset_delta + 1 but only offset_delta; setting the
                     * implicit frame offset to -1 allow the use of the
                     * "offset_delta + 1" rule in all cases
                     */
                    frameOffset = -1;
                }
                v = codeStart;
                Label l;
                while (v < codeEnd) {
                    w = v - codeStart;

                    l = labels[w];
                    if (l != null) {
                        mv.visitLabel(l);
                        if (!skipDebug && l.line > 0) {
                            mv.visitLineNumber(l.line, l);
                        }
                    }

                    while (frameLocal != null
                            && (frameOffset == w || frameOffset == -1))
                    {
                        // if there is a frame for this offset,
                        // makes the visitor visit it,
                        // and reads the next frame if there is one.
                        if (!zip || unzip) {
                            mv.visitFrame(Opcodes.F_NEW,
                                    frameLocalCount,
                                    frameLocal,
                                    frameStackCount,
                                    frameStack);
                        } else if (frameOffset != -1) {
                            mv.visitFrame(frameMode,
                                    frameLocalDiff,
                                    frameLocal,
                                    frameStackCount,
                                    frameStack);
                        }

                        if (frameCount > 0) {
                            int tag, delta, n;
                            if (zip) {
                                tag = b[stackMap++] & 0xFF;
                            } else {
                                tag = MethodWriter.FULL_FRAME;
                                frameOffset = -1;
                            }
                            frameLocalDiff = 0;
                            if (tag < MethodWriter.SAME_LOCALS_1_STACK_ITEM_FRAME)
                            {
                                delta = tag;
                                frameMode = Opcodes.F_SAME;
                                frameStackCount = 0;
                            } else if (tag < MethodWriter.RESERVED) {
                                delta = tag
                                        - MethodWriter.SAME_LOCALS_1_STACK_ITEM_FRAME;
                                stackMap = readFrameType(frameStack,
                                        0,
                                        stackMap,
                                        c,
                                        labels);
                                frameMode = Opcodes.F_SAME1;
                                frameStackCount = 1;
                            } else {
                                delta = readUnsignedShort(stackMap);
                                stackMap += 2;
                                if (tag == MethodWriter.SAME_LOCALS_1_STACK_ITEM_FRAME_EXTENDED)
                                {
                                    stackMap = readFrameType(frameStack,
                                            0,
                                            stackMap,
                                            c,
                                            labels);
                                    frameMode = Opcodes.F_SAME1;
                                    frameStackCount = 1;
                                } else if (tag >= MethodWriter.CHOP_FRAME
                                        && tag < MethodWriter.SAME_FRAME_EXTENDED)
                                {
                                    frameMode = Opcodes.F_CHOP;
                                    frameLocalDiff = MethodWriter.SAME_FRAME_EXTENDED
                                            - tag;
                                    frameLocalCount -= frameLocalDiff;
                                    frameStackCount = 0;
                                } else if (tag == MethodWriter.SAME_FRAME_EXTENDED)
                                {
                                    frameMode = Opcodes.F_SAME;
                                    frameStackCount = 0;
                                } else if (tag < MethodWriter.FULL_FRAME) {
                                    j = unzip ? frameLocalCount : 0;
                                    for (k = tag
                                            - MethodWriter.SAME_FRAME_EXTENDED; k > 0; k--)
                                    {
                                        stackMap = readFrameType(frameLocal,
                                                j++,
                                                stackMap,
                                                c,
                                                labels);
                                    }