Implement SHA1 checksums and optional download for documents

2 files changed, 32 insertions, 13 deletions

diff --git a/pcb/documents.tsv b/pcb/documents.tsv
index 087fc3d..2544bc3 100644
--- a/pcb/documents.tsv
+++ b/pcb/documents.tsv
@@ -1,7 +1,7 @@
-Name	URL
-IRF840A_datasheet.pdf	https://www.infineon.com/dgdl/Infineon-SPP_A04N50C3-DS-v02_09-en.pdf?fileId=db3a304412b407950112b42cfc9247e4
-IR2127_datasheet.pdf	https://www.infineon.com/dgdl/Infineon-ir2127-DS-v01_00-EN.pdf?fileId=5546d462533600a4015355c868861696
-L7805CV_datasheet.pdf	https://www.st.com/resource/en/datasheet/l78.pdf
-STM32F103C8T6_datasheet.pdf	https://www.st.com/resource/en/datasheet/stm32f103c8.pdf
-STM32F103C8T6_reference_manual.pdf	https://www.st.com/resource/en/reference_manual/rm0008-stm32f101xx-stm32f102xx-stm32f103xx-stm32f105xx-and-stm32f107xx-advanced-armbased-32bit-mcus-stmicroelectronics.pdf
-STM32F103C8T6_programming_manual.pdf	https://www.st.com/resource/en/programming_manual/pm0056-stm32f10xxx20xxx21xxxl1xxxx-cortexm3-programming-manual-stmicroelectronics.pdf
+Name	URL	SHA1
+IRF840A_datasheet.pdf	https://www.infineon.com/dgdl/Infineon-SPP_A04N50C3-DS-v02_09-en.pdf?fileId=db3a304412b407950112b42cfc9247e4	02a02be50e00a6d88f29ed5390b41e00ff18f377
+IR2127_datasheet.pdf	https://www.infineon.com/dgdl/Infineon-ir2127-DS-v01_00-EN.pdf?fileId=5546d462533600a4015355c868861696	08b47f0b650bb8aee3aa8ab94e928d3ef6a2d23b
+L7805CV_datasheet.pdf	https://www.st.com/resource/en/datasheet/l78.pdf	751385ffecbf704a5b48e3f0338207634aba3bbe
+STM32F103C8T6_datasheet.pdf	https://www.st.com/resource/en/datasheet/stm32f103c8.pdf	cef117449ee60efe80f4b927569ee03f5a8ed0b9
+STM32F103C8T6_reference_manual.pdf	https://www.st.com/resource/en/reference_manual/rm0008-stm32f101xx-stm32f102xx-stm32f103xx-stm32f105xx-and-stm32f107xx-advanced-armbased-32bit-mcus-stmicroelectronics.pdf	adbb749261c5db0ecbec95c9e63071737d91a878
+STM32F103C8T6_programming_manual.pdf	https://www.st.com/resource/en/programming_manual/pm0056-stm32f10xxx20xxx21xxxl1xxxx-cortexm3-programming-manual-stmicroelectronics.pdf	befb4158d0f1317f411c829adcadeebf09e2d7a8
diff --git a/pcb/download.sh b/pcb/download.sh
index dfe1be9..4aa5f49 100755
--- a/pcb/download.sh
+++ b/pcb/download.sh
@@ -1,11 +1,15 @@
 #!/bin/sh
 
 
+# This script creates a cache directory and downloads all external documents
+# to this folder. In addition the SHA1 checksums are checked and the user is
+# warned if a checksum does not match.
+
+
 # constants
 DOCUMENTS_FILE='documents.tsv'
 CACHE='./cache'  # target folder for all downloads
 
-
 # strip first line of table file
 TABLE=$(sed '1d' "${DOCUMENTS_FILE}")
 
@@ -18,14 +22,29 @@ do
 
 	FILENAME=$(echo "$line" | awk -F '\t' '{print $1}')  # column 1 -> filename
 	URL=$(echo "$line" | awk -F '\t' '{print $2}')       # column 2 -> URL
+	SHA1=$(echo "$line" | awk -F '\t' '{print $3}')      # column 3 -> SHA1 hash
+
+	FILEPATH="${CACHE}/${FILENAME}"
+
+	# download file if it does not exist in cache
+	if [ ! -f "${FILEPATH}" ]
+	then
+		printf 'Downloading %s ...' "${FILEPATH}"
+		if wget -qO "${FILEPATH}" "${URL}" 2> /dev/null
+		then
+			printf " ok\n"        # if wget returned with exit code 0
+		else
+			printf " error!\n"    # in any other case
+		fi
+	fi
 
-	# actual download of one document
-	printf 'Downloading %s/%s ...' "${CACHE}" "${FILENAME}"
-	if wget -qO "${CACHE}/${FILENAME}" "${URL}" 2> /dev/null
+	# generate and compare SHA1 checksum of file
+	printf 'Checking SHA1 sum of %s ...' "${FILEPATH}"
+	if printf '%s %s' "${SHA1}" "${FILEPATH}" | sha1sum -c - > /dev/null 2>&1
 	then
-		printf " ok\n"        # if wget returned with exit code 0
+		echo " ok"
 	else
-		printf " error!\n"    # in any other case
+		echo " file changed!"
 	fi
 
 done