From e497fcd9d69f2ba6b8672e430ee273db4afbea17 Mon Sep 17 00:00:00 2001

From: Michael Drake <michael.drake@codethink.co.uk>

Date: Thu, 7 Jun 2018 11:01:37 +0100

Subject: [PATCH 5/9] lsusb: Split out routine that fetches value for given

 field.

Field value lookup was done in multiple places, so it's useful

as a helper function.

Signed-off-by: Michael Drake <michael.drake@codethink.co.uk>

---

 desc-dump.c | 106 +++++++++++++++++++++++++++++++++---------------------------

 1 file changed, 58 insertions(+), 48 deletions(-)

diff --git a/desc-dump.c b/desc-dump.c

index 9210df7..393ff70 100644

--- a/desc-dump.c

+++ b/desc-dump.c

@@ -2,7 +2,7 @@

 /*

  * USB descriptor dumping

  *

- * Copyright (C) 2017 Michael Drake <michael.drake@codethink.co.uk>

+ * Copyright (C) 2017-2018 Michael Drake <michael.drake@codethink.co.uk>

  */

 #include "config.h"

@@ -109,6 +109,57 @@ static unsigned long long get_n_bytes_as_ull(

 	return ret;

 }

+/**

+ * Get the size of a descriptor field in bytes.

+ *

+ * Normally the size is provided in the entry's size parameter, but some

+ * fields have a variable size, with the actual size being stored in as

+ * the value of another field.

+ *

+ * \param[in] buf    Descriptor data.

+ * \param[in] desc   First field in the descriptor definition array.

+ * \param[in] entry  The descriptor definition field to get size for.

+ * \return Size of the field in bytes.

+ */

+static unsigned int get_entry_size(

+		const unsigned char *buf,

+		const struct desc *desc,

+		const struct desc *entry);

+

+/**

+ * Read a value from a field of given name.

+ *

+ * \param[in] buf    Descriptor data.

+ * \param[in] desc   First field in the descriptor definition array.

+ * \param[in] field  The name of the field to get the value for.

+ * \return The value from the given field.

+ */

+static unsigned long long get_value_from_field(

+		const unsigned char *buf,

+		const struct desc *desc,

+		const char *field)

+{

+	size_t offset = 0;

+	const struct desc *current;

+	unsigned long long value = 0;

+

+	/* Search descriptor definition array for the field who's value

+	 * gives the value of the entry we're interested in. */

+	for (current = desc; current->field != NULL; current++) {

+		if (strcmp(current->field, field) == 0) {

+			value = get_n_bytes_as_ull(buf, offset,

+					current->size);

+			break;

+		}

+

+		/* Keep track of our offset in the descriptor data

+		 * as we look for the field we want. */

+		offset += get_entry_size(buf, desc, current);

+	}

+

+	return value;

+}

+

 /**

  * Dump a number as hex to stdout.

  *

@@ -270,18 +321,7 @@ static void value_renderer(

 	}

 }

-/**

- * Get the size of a descriptor field in bytes.

- *

- * Normally the size is provided in the entry's size parameter, but some

- * fields have a variable size, with the actual size being stored in as

- * the value of another field.

- *

- * \param[in] buf    Descriptor data.

- * \param[in] desc   First field in the descriptor definition array.

- * \param[in] entry  The descriptor definition field to get size for.

- * \return Size of the field in bytes.

- */

+/* Documented at forward declaration above. */

 static unsigned int get_entry_size(

 		const unsigned char *buf,

 		const struct desc *desc,

@@ -292,24 +332,7 @@ static unsigned int get_entry_size(

 	if (entry->size_field != NULL) {

 		/* Variable field length, given by `size_field`'s value. */

-		size_t offset = 0;

-

-		/* Search descriptor definition array for the field who's value

-		 * gives the size of the entry we're interested in. */

-		for (current = desc; current->field != NULL; current++) {

-			if (strcmp(current->field, entry->size_field) == 0) {

-				/* Found the field who's value gives us the

-				 * size of, so read that field's value out of

-				 * the descriptor data buffer. */

-				size = get_n_bytes_as_ull(buf, offset,

-						current->size);

-				break;

-			}

-

-			/* Keep track of our offset in the descriptor data

-			 * as we look for the field we want. */

-			offset += get_entry_size(buf, desc, current);

-		}

+		size = get_value_from_field(buf, desc, entry->size_field);

 	}

 	if (size == 0) {

@@ -347,27 +370,14 @@ static unsigned int get_array_entry_count(

 	if (array_entry->array.length_field1) {

 		/* We can get the array size from the length_field1. */

-		size_t offset = 0;

-		for (current = desc; current->field != NULL; current++) {

-			if (strcmp(current->field, array_entry->array.length_field1) == 0) {

-				entries = get_n_bytes_as_ull(buf, offset, current->size);

-				break;

-			}

+		entries = get_value_from_field(buf, desc,

+				array_entry->array.length_field1);

-			offset += get_entry_size(buf, desc, current);

-		}

-		offset = 0; /* skip first three common 1-byte fields */

 		if (array_entry->array.length_field2 != NULL) {

 			/* There's a second field specifying length.  The two

 			 * lengths are multiplied. */

-			for (current = desc; current->field != NULL; current++) {

-				if (strcmp(current->field, array_entry->array.length_field2) == 0) {

-					entries *= get_n_bytes_as_ull(buf, offset, current->size);

-					break;

-				}

-

-				offset += get_entry_size(buf, desc, current);

-			}

+			entries *= get_value_from_field(buf, desc,

+					array_entry->array.length_field2);

 		}

 		/* If the bits flag is set, then the entry count so far

-- 

2.14.4