+/* BEGINNING of flags that apply to opj_flag_t */
+/** We hold the state of individual data points for the T1 encoder using
+ * a single 32-bit flags word to hold the state of 4 data points. This corresponds
+ * to the 4-point-high columns that the data is processed in.
+ *
+ * These \#defines declare the layout of a 32-bit flags word.
+ *
+ * This is currently done for encoding only.
+ * The values must NOT be changed, otherwise this is going to break a lot of
+ * assumptions.
+ */
+
+/* SIGMA: significance state (3 cols x 6 rows)
+ * CHI: state for negative sample value (1 col x 6 rows)
+ * MU: state for visited in refinement pass (1 col x 4 rows)
+ * PI: state for visited in significance pass (1 col * 4 rows)
+ */
+
+#define T1_SIGMA_0 (1U << 0)
+#define T1_SIGMA_1 (1U << 1)
+#define T1_SIGMA_2 (1U << 2)
+#define T1_SIGMA_3 (1U << 3)
+#define T1_SIGMA_4 (1U << 4)
+#define T1_SIGMA_5 (1U << 5)
+#define T1_SIGMA_6 (1U << 6)
+#define T1_SIGMA_7 (1U << 7)
+#define T1_SIGMA_8 (1U << 8)
+#define T1_SIGMA_9 (1U << 9)
+#define T1_SIGMA_10 (1U << 10)
+#define T1_SIGMA_11 (1U << 11)
+#define T1_SIGMA_12 (1U << 12)
+#define T1_SIGMA_13 (1U << 13)
+#define T1_SIGMA_14 (1U << 14)
+#define T1_SIGMA_15 (1U << 15)
+#define T1_SIGMA_16 (1U << 16)
+#define T1_SIGMA_17 (1U << 17)
+
+#define T1_CHI_0 (1U << 18)
+#define T1_CHI_0_I 18
+#define T1_CHI_1 (1U << 19)
+#define T1_CHI_1_I 19
+#define T1_MU_0 (1U << 20)
+#define T1_PI_0 (1U << 21)
+#define T1_CHI_2 (1U << 22)
+#define T1_CHI_2_I 22
+#define T1_MU_1 (1U << 23)
+#define T1_PI_1 (1U << 24)
+#define T1_CHI_3 (1U << 25)
+#define T1_MU_2 (1U << 26)
+#define T1_PI_2 (1U << 27)
+#define T1_CHI_4 (1U << 28)
+#define T1_MU_3 (1U << 29)
+#define T1_PI_3 (1U << 30)
+#define T1_CHI_5 (1U << 31)
+#define T1_CHI_5_I 31
+
+/** As an example, the bits T1_SIGMA_3, T1_SIGMA_4 and T1_SIGMA_5
+ * indicate the significance state of the west neighbour of data point zero
+ * of our four, the point itself, and its east neighbour respectively.
+ * Many of the bits are arranged so that given a flags word, you can
+ * look at the values for the data point 0, then shift the flags
+ * word right by 3 bits and look at the same bit positions to see the
+ * values for data point 1.
+ *
+ * The \#defines below help a bit with this; say you have a flags word
+ * f, you can do things like
+ *
+ * (f & T1_SIGMA_THIS)
+ *
+ * to see the significance bit of data point 0, then do
+ *
+ * ((f >> 3) & T1_SIGMA_THIS)
+ *
+ * to see the significance bit of data point 1.
+ */
+
+#define T1_SIGMA_NW T1_SIGMA_0
+#define T1_SIGMA_N T1_SIGMA_1
+#define T1_SIGMA_NE T1_SIGMA_2
+#define T1_SIGMA_W T1_SIGMA_3
+#define T1_SIGMA_THIS T1_SIGMA_4
+#define T1_SIGMA_E T1_SIGMA_5
+#define T1_SIGMA_SW T1_SIGMA_6
+#define T1_SIGMA_S T1_SIGMA_7
+#define T1_SIGMA_SE T1_SIGMA_8
+#define T1_SIGMA_NEIGHBOURS (T1_SIGMA_NW | T1_SIGMA_N | T1_SIGMA_NE | T1_SIGMA_W | T1_SIGMA_E | T1_SIGMA_SW | T1_SIGMA_S | T1_SIGMA_SE)
+
+#define T1_CHI_THIS T1_CHI_1
+#define T1_CHI_THIS_I T1_CHI_1_I
+#define T1_MU_THIS T1_MU_0
+#define T1_PI_THIS T1_PI_0
+#define T1_CHI_S T1_CHI_2