public final BigDecimal readBigDecimal()

in core/src/main/java/com/alibaba/fastjson2/JSONReaderUTF16.java [4077:4284]
184 lines of code
80 McCabe index (conditional complexity)

    public final BigDecimal readBigDecimal() {
        boolean valid = false;
        final char[] chars = this.chars;
        char ch = this.ch;
        int offset = this.offset;
        boolean value = false;

        BigDecimal decimal = null;
        int quote = '\0';
        if (ch == '"' || ch == '\'') {
            quote = ch;
            ch = chars[offset++];

            if (ch == quote) {
                this.ch = offset == end ? EOI : chars[offset++];
                this.offset = offset;
                nextIfComma();
                return null;
            }
        }

        final int start = offset;
        if (ch == '-') {
            negative = true;
            ch = chars[offset++];
        } else {
            negative = false;
            if (ch == '+') {
                ch = chars[offset++];
            }
        }

        valueType = JSON_TYPE_INT;
        boolean overflow = false;
        long longValue = 0;
        while (ch >= '0' && ch <= '9') {
            valid = true;
            if (!overflow) {
                long r = longValue * 10;
                if ((longValue | 10) >>> 31 == 0L || (r / 10 == longValue)) {
                    longValue = r + (ch - '0');
                } else {
                    overflow = true;
                }
            }

            if (offset == end) {
                ch = EOI;
                offset++;
                break;
            }
            ch = chars[offset++];
        }

        if (longValue < 0) {
            overflow = true;
        }

        this.scale = 0;
        if (ch == '.') {
            valueType = JSON_TYPE_DEC;
            ch = chars[offset++];
            while (ch >= '0' && ch <= '9') {
                valid = true;
                this.scale++;
                if (!overflow) {
                    long r = longValue * 10;
                    if ((longValue | 10) >>> 31 == 0L || (r / 10 == longValue)) {
                        longValue = r + (ch - '0');
                    } else {
                        overflow = true;
                    }
                }

                if (offset == end) {
                    ch = EOI;
                    offset++;
                    break;
                }
                ch = chars[offset++];
            }
        }

        int expValue = 0;
        if (ch == 'e' || ch == 'E') {
            boolean negativeExp;
            ch = chars[offset++];
            if ((negativeExp = ch == '-') || ch == '+') {
                ch = chars[offset++];
            }

            while (ch >= '0' && ch <= '9') {
                valid = true;
                int byteVal = (ch - '0');
                expValue = expValue * 10 + byteVal;
                if (expValue > MAX_EXP) {
                    throw new JSONException("too large exp value : " + expValue);
                }

                if (offset == end) {
                    ch = EOI;
                    offset++;
                    break;
                }
                ch = chars[offset++];
            }

            if (negativeExp) {
                expValue = -expValue;
            }

            this.exponent = (short) expValue;
            valueType = JSON_TYPE_DEC;
        }

        if (offset == start) {
            if (ch == 'n' && chars[offset++] == 'u' && chars[offset++] == 'l' && chars[offset++] == 'l') {
                if ((context.features & Feature.ErrorOnNullForPrimitives.mask) != 0) {
                    throw new JSONException(info("long value not support input null"));
                }

                wasNull = true;
                value = true;
                ch = offset == end ? EOI : chars[offset];
                offset++;
                valid = true;
            } else if (ch == 't' && offset + 3 <= end && chars[offset] == 'r' && chars[offset + 1] == 'u' && chars[offset + 2] == 'e') {
                valid = true;
                offset += 3;
                value = true;
                decimal = BigDecimal.ONE;
                ch = offset == end ? EOI : chars[offset];
                offset++;
            } else if (ch == 'f' && offset + 4 <= end
                    && chars[offset] == 'a'
                    && chars[offset + 1] == 'l'
                    && chars[offset + 2] == 's'
                    && chars[offset + 3] == 'e') {
                valid = true;
                offset += 4;
                decimal = BigDecimal.ZERO;
                value = true;
                ch = offset == end ? EOI : chars[offset];
                offset++;
            } else if (ch == '{' && quote == 0) {
                JSONObject jsonObject = new JSONObject();
                readObject(jsonObject, 0);
                wasNull = false;
                return decimal(jsonObject);
            } else if (ch == '[' && quote == 0) {
                List array = readArray();
                if (!array.isEmpty()) {
                    throw new JSONException(info());
                }
                wasNull = true;
                return null;
            }
        }

        int len = offset - start;

        if (quote != 0) {
            if (ch != quote) {
                String str = readString();
                try {
                    return TypeUtils.toBigDecimal(str);
                } catch (NumberFormatException e) {
                    throw new JSONException(info("cast to decimal error " + str), e);
                }
            } else {
                ch = offset >= end ? EOI : chars[offset++];
            }
        }
        if (!value) {
            if (expValue == 0 && !overflow && longValue != 0) {
                decimal = BigDecimal.valueOf(negative ? -longValue : longValue, scale);
                value = true;
            }

            if (!value) {
                decimal = TypeUtils.parseBigDecimal(chars, start - 1, len);
            }

            if (ch == 'L' || ch == 'F' || ch == 'D' || ch == 'B' || ch == 'S') {
                ch = offset >= end ? EOI : chars[offset++];
            }
        }

        while (ch <= ' ' && ((1L << ch) & SPACE) != 0) {
            ch = offset == end ? EOI : chars[offset++];
        }

        if (comma = (ch == ',')) {
            // next inline
            ch = offset == end ? EOI : chars[offset++];
            while (ch <= ' ' && ((1L << ch) & SPACE) != 0) {
                ch = offset == end ? EOI : chars[offset++];
            }
        }

        if (!valid) {
            throw new JSONException(info("illegal input error"));
        }

        this.ch = ch;
        this.offset = offset;
        return decimal;
    }